To win games in gruesome one day tournaments:
a) Work on your endgames so that you can simplify your games and win all better or equal endgames.
b) Choose the safe way (when you can) to economize energy.
c) Take care of yourself.(Relax, eat and drink healthy.)
d) Put your Queen on h5 early.
(Just kidding, though sometimes it works.)
I will also participate at a very important tournament (Unicorn Open)in about 1 month, there will be a lot of strong players few IM and GM's and I really want to make a good impression...
How I prepare:
I first analyse some games played last year. Then I focus on the openings that were mostly played and try to add some to my repertoire.
After doing this I return to my chess books and read, read, read.
Hope it helped,
Cosmin
In order to prepare for G/30, try playing some G/5. I wouldn't recommend this as prep in the days leading up to the tournament, but if you are thinking in terms of months, I would do this. Don't worry about playing the utmost quality in G/5, just play the best you can in the time alotted. Don't allow yourself to make the excuse that you didn't have enough time to find the best move, you're not trying to find the best move, you're trying to win the game.
The idea is that if G/30 is the fastest time control you play it will always seem very fast to you. When you get into a situation up a rook with 2 minutes on your clock you will continue to try to find the best moves and get flagged rather than just winning the game like a regular blitz player would. You will gain blitz experience quickly at G/5 (you can play 6 times as many games at this time control than at G/30). Soon you will become comfortable converting your winning games with a dwindling clock and the prospect of doing this after a long fight in G/30 will no longer be so daunting.
I have been playing in OTB tournaments for over 30 years, and what works best for me is to get plenty of rest the week before don't go in playing tired. Play openings you are comfortable with and don't rush your moves. Good Luck
Well, since you know the players in your club you should also have a fair idea of what openings and variations they play. Use this information! Look over the games you played with the people you expect to see at the tournament. If the same openings come up you really shouldnt be making any errors. If you made errors in opening in previous games against these guys now is the time to rectify that. Use your copy of NCO or computer database to see what you should have done. You will be streets ahead of your opponent as this info will be fresh in your head.
If you are playing a formal tournament at some stage i recommend you bring a laptop, a good database and find out who your opponent is for the following round. Nothing like being prepared!
To be honest if you are not rated above 2000 it is was you do AFTER the tournament that really matters. Best of luck with it, and let us know how it goes. Maybe the next comments we post to you will be in the game showcase! 
The best way to prepare for a tournament like this is to relax. Don't look at the result but at how you play. Last time you lost winning positions, play practice positions where you have an advantage but not a forced line. You have problems with the clock so create a time plan, you have an opening plan and correct use of time is as important as having a correctly played opening.
For a completely different thought, does your opening plan match the time limit? Do you want to spend 20+ moves manuvering in the KIA vs the sicilian or do you need a more direct approach (Wing, Smith/Morra, Moscow, Rosslissimo, Grand Prix) , same for Pirc, etc.
I have a club tournament in a few weeks. It’s an informal (unrated) affair with 30 min (per side) games. And I am an informal (unrated) player who has only played these club affairs. My goal is to avoid the poor result of our last tournament, where I lost 2 winnable games on time and one opponent won both the most brilliant game award and best upset award!
To prepare, a few weeks ago I’ve started cutting back on my play here, stopped reading my current chess book (the art of attack chess) and started playing more 30 min games on FICS. While I have not studied any openings in any debth, I still try to stick to the same basic openings: King’s Gambit/KIA (against the French)/Sicilian with white and Pirc/Gruenfeld with black. I also started studying tactics on this cite more intensely.
How do you prepare (or advise others to prepare) for action tournaments like these? Should I be more focused on memorizing a few more opening lines (or different openings altogether) or stay the course by brushing up on my tactics? Frankly, it’s likely too late to change my approach now. But we will have another in a few months and I might even work up the nerve to try a formal (rated) local tournament.
Moreover, having found little advice on-line, I thought I’d seek the chess wisdom of this community. Thanks in advance for any thoughts or advice.