As i've started operating more as a judge and less as a player at my LGS I've run into this problem twice where my calls were deemed stupid and/or wrong for what i suspect are personal reasons.

The first time involves a player that is kind of a know-it-all, who after calling me over to ask if his opponent can respond to detention sphere's etb by activating the targeted creature's (heliod's) ability. When i ruled that he can, he disregarded my ruling and attempted to proceed as if I had said nothing. His opponent and a few who were watching validated my ruling, and he then listened to it.

The second instance was at a modern event, a player called for a judge and seemed quite unsure when I approached, going as far as to propose the use of a friend of his' (a L1 judge) rulings instead, the TO declined and I said I'd gladly accept his friend's council, made a ruling on norin the wary which his friend confirmed, and went on with judging.

My question is whether there is any better way to respond to these sorts of situations with difficult players, I honestly was a little nervous in both situations and questioned myself a decent bit, and would rather learn proper procedures before I show off how inexperienced I am.

The first advice is, of course, to study and be sure of your rullings.
That is not something you will be able to achieve overnight, so get to
work on that :P

I too am a bit shy and can't deal very well with confrontation so I've
struggled a bit with that kind of scenarios. Something you could to
reassure yourself and make sure the interaction with the player goes the
way you want is to say to the player that you are tournament personnel
and the official authority. If they don't like your rulling they can
discuss with you later, but you have the final call and they should take
it and continue playing. Insist on them continuing with the game and not
dabble on the rulling after you've given it.

There a few subtle tricks to impose your figure as a judge. One that I
like a lot is to crouch or sit when I approach a table, so that I'm
levelled with the players, sometimes even lower than them. If the
rulling is complicated or they argue, you can then stand up and tower
over the players, subconciously imposing your authority.

Gaining confidence and overcomming complicated players is not an easy
thing to do. If you're concious of it and take steps you'll get there.
Also, something that you will see works is, as time passes and you
cement your role as a judge on the community, all other players will
respect you and your rullings. That will make the more rebellious ones
fold too.

Keep up the good work!

Gregory: Most of us have learned from our mistakes more than our successes. Any level judge can tell you stories of when they were wrong and how it turned out. For me, it causes near-sleepless nights. But I'm told that what we have to do is at least act confident in our rulings, so that's what I do. The more I read and study, the more confident I am. For me, I greatly regret telling my FNM players one night that a single attacker controlled by one teammate would get the Exalted benefit from teammate's creatures in 2HG. Oh, the agony. But I let the TO know what I did so he could fix it in subsequent games when I wasn't around.

In your first example, you did the right ruling, but you have to assert yourself. If the player has disagreed with you, you may try explaining the principle behind the ruling, possibly giving another example. A short explanation of triggered abilities with targets, activated abilities, and the stack should have sufficed, but the player cannot continue playing the way he did. This may fall under MTR 5.4 Unsporting Conduct “failing to follow the instructions of a tournament official.”

If we are unsure of a ruling we are called to make, we must ask the players to wait while we look into it, do our research, and then report our findings. This happened to me when a player cast a spell with Cipher and had no creatures to encode onto. My research showed that the ability includes the word MAY, so the spell went to the graveyard instead of exile. That said, the players must first hear what we have to say in a ruling. Only after they've heard our ruling can they appeal to the Head Judge, but not a different Floor Judge.

I only wanted to add a bit to the previous excellent answers to your concerns. Note that most of the correct attitude, tricks and experience to deal with these conflictive situations are applicable to a lot of different scenarios in real life, not only as a Magic judge :)

There are two things that, more than anything else, will make players respect your rulings and judgment: the first is to give your rulings with confidence and clarity, and the second is recognizing your mistakes as early as possible.

For the first, experience is the only way. You need to give lots of rulings, read the rules several times (preferably in the context of a card interaction) and learn by heart how certain commonly used cards work. This will give you confidence in your answers and players will sense it. Having a copy of the CR and Gatherer in your cellphone and being familiar enough with its structure to be able to show the players the appropriate rule is great (this is a great app, BTW).

The second is much easier to achieve. Give your ruling and ask them to continue playing according to it. And then immediately go double-check your answer. If you were wrong, go back to the table ASAP and let the players know that you made a mistake and provide the right answer. Fix the game state if needed, but try to avoid confronting them. Everyone can make mistakes; the right thing is to learn from them to avoid repeats and owning up when they occur.

I like most of the advices a lot.
Still, I disagree with Claudio regarding the second advice.

Give your ruling and ask them to continue playing according to it. And then immediately go double-check your answer. If you were wrong, go back to the table ASAP and let the players know that you made a mistake and provide the right answer. Fix the game state if needed, but try to avoid confronting them. Everyone can make mistakes; the right thing is to learn from them to avoid repeats and owning up when they occur.

I think confidence is something crucial to the job of judging, but is not more important than giving a correct answer. I think, the main reason judges don't recieve respect are mistakes, and we should put a lot of effort in not commiting them. That doesn't mean you can't commit mistakes: everyone can make poor decision sometimes, and is important to let the players know that you made it, because of at least 2 reasons: (1) humility is important in this job, (2) they will think your rulling is ok and that could mean more mistakes in the future.

When players notice hard inconsitency between rullings, the judge program looses credibility. Therefore, I don't recommend judges to give provisional answers if they are not sure and they have ways to easily confirm it. That coud have terrible consequences for the match, the education of players and the judge program as a whole. As a player, I preffer a 100 times a judge that takes a minute to ask another one to be sure about something, than a judge that gives me a poor rulling just to show confidence, and then corrects himself when the mistake is most likely irreparable.

I might have given the wrong impression due to a poor choice of words.

I'm not advocating giving a quick answer for the sake of it. I am saying that you should check your answers even after giving them (and even if you felt sure of what you ruled). That's the only way to catch mistakes early and you should always get back to the players if you made a mistake, apologize and explain the proper ruling.

My phrasing was mostly a concession to judges not always having the option of double checking their rulings before giving them. Searching the rules in the CR can take too much time sometimes; or you may be just in the middle of some other task and be the only judge in the event. These things happen and it is part of our jobs to learn to deal with them.

My apologies for any misunderstandings that might have arisen.

Thanks for the clarification Claudio, and sorry for my missunderstanding :)

Also, don't be afraid of looking things up before you give a ruling. If you're the only judge, and you aren't sure, it's much better to tell the players that you are going to double check the rules relating to their question, you'll give them extra time and then quickly check the answer (or even ask in http://chat.magicjudges.org/mtgrules/).

If the players see you will check rules before answering more complex or less common issues, they may feel more confident when you give a ruling you know the answer to.

I would also agree that even if you are sure of your answer, look it up and confirm after giving your answer.