Anything that doesn't fall under page-worthy material (generally hints, tips and tricks) can be found here.
The classic Square combination of A + B + L + R (or R1 + R2 + L1 + L2 + Start + Select, if you're a PSX gamer) will soft-reset the game without having to go near the console. Not necessarily a secret, but useful for those boss fights that you know you're never going to win.
Once you get to Guardia Forest in the Middle Ages, look about for a rustling bush. (Fnar.) Examine it, and a Nu will jump out and flee, leaving behind a Shelter. All that's needed is a little rinse and repeat, and hey, presto, you're set for shelter for the game.
Don't we all? If you go to the End of Time, talk to a character and say you'll take them with you (if you don't actually want to, just back out of the party selection screen). This will cause said character's theme to play on a loop as long as you're in the End of Time. For the record, Magus' theme is the best.
Getting high-powered equipment early in the game, or at least, equipment that won't be out of date within the next hour of gameplay, is a near impossible feat in Chrono Trigger. Fortunately, hitting the enemy isn't the only way to deal damage, and there are some good ways to build up Technique Points early on.
The best place, bar none, for TP is on Mount Woe. There are a few Rubble enemies which go for 100TP. Each. Not to mention 1000EXP to go with it. Go up, take them all out, and leave the Mountain. When you return, all will be restored, and even the highest levelled Techniques will be yours in a short amount of time. Unfortunately, said location becomes unavailable... pretty quickly indeed. So if you're gonna do it, do it as soon as possible.
What, you want more? Ever think that our coverage is so awesome we only need four miscellaneous tricks? If not, stop complaining read up on our FAQ.