OK! congratulations, OTB Chess is just a tough sport...to... enjoy! 
First OTB tournament
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Forgot who gave this tip (Heisman or Silman maybe?) but during your turn you're calculating moves and such but on your opponents turn try to assess what's going on in general, i.e. a strategic assessment. This means things like pawn structure, king safety, open files, active pieces and things like this. If you're just beginning that might seem hard, but in general you're just asking yourself which side is better and then trying to figure out why you like that side (by finding the pluses and minuses for each player).
Of course during your opponent's turn you'll probably also check a few likely moves they might make and do some calculations.
Yes, it's important to learn how to manage your clock! Ending in an hour is too fast :) One mistake is to focus too much on the depth of calculation when what's important is accuracy. Accuracy is what takes players so long in tournament games. So when considering a move, try hard to visualize the move as if it were already made on the board... just that one move... don't do anything else yet! (The temptation is to keep calculating especially if the move you want to make is a capture). Now work on finding your opponent's best or perhaps most annoying reply. As a minimum you have to consider all the checks and captures they might make in response to your move. Try to never ever start off by looking at the move you'd like to see them make.
You might see right away that they have to recapture, but if you don't check every time it means you'll eventually run into a nasty surprise that will likely lose you the game on the spot.
So a very useful training method that increases both calculation ability and checking for tactics is... you guessed it, solving lots of tactical puzzles.
A good author on strategy is Silman. Recommend his Amateur's Mind and Reassess books.
Well I just completed 5 games at 90/min + 30 sec games this weekend for the first time.
I played the last class as a unrated player since I am beginning. I won 2 out of the 5 games and I guess the reason for the post concerns the thinking process for such long games.
I basically realized that playing such long games enables us to reflect and evaluate more. However I realized as well is that at my level, I can only evaluate so much and not necessarily know what is the best move etc... Upon analyzing my games with chess base afterwards, I realized I could of won an extra game but I played it wrong. But that's chess. I guess what I've learned from this experience will be to improve on my analysis, try to look more at the opponents threats and try to see more that just 2 or three moves ahead. And finally not to play so fast. A couple of my games were completed in an hour and three of them around two hours.