What's with the blued-in techs in Lloyd/Genis/Colette/whatever's tech menu?

Check the Tech Skills page. Blue techs require you to cast a spell/do some other tech fifty times before you can learn that one. i.e., if you want Genis to learn Eruption, he needs to cast Fire Ball fifty times. More information in question two.

OK, I get the whole fifty times thing, but my character still hasn't learned the tech! AUGH!

Patience, grasshopper. No game is perfect. Try ordering the character to use the spell manually several times in a row in the same battle. Often enough, this will trigger the learning of the spell. If not, well... keep trying. This "bug" (dunno if it's really a bug, but it sure seems like it) seems to occur most often if you've used the spell more than fifty times before the blue tech appears in your menu. Also, if it's a "combination" tech (i.e., like Demonic Thrust requires you to use both Demon Fang and Sonic Thrust 50+ times) that your character refuses to learn, you might want to use Demon Fang and Sonic Thrust (or whatever the two requirements are) manually several times in one battle, and if that doesn't work, do that and use any deriviations (i.e., Double Demon Fang, Super Sonic Thrust, etc.) of those techs (that aren't also combo techs) manually several times in one battle. If it's a spell like Explosion that's stuck as blued-in, then you'll want to use Eruption and Fireball (or whatever the requirements are) manually several times in one battle.

I just got Zelos/Presea/whomever... and he/she/it/cheesecake refuses to learn his blued-in techs! WHYYYYYY???

Check Zelos/Presea/whatever's T vs. S gauge in your menu. More than likely, when you first get him he's neither one nor the other, but stuck in the middle. This will pretty much prevent him from learning anything new. Equip him with the Technical Ring to force him to the T side, or give him a bunch of T- or S-type EX-Skills, and then he'll start learning new techs if you follow the advice from the previous questions (the gauge has to be in the red for any skills to be learned).

Why can't I summon Undine/Efreet/whatever other summon besides Corrine in battle?

Sheena has to be in Overlimit (i.e., when she starts being surrounded by darkness after getting smacked around a lot) to be able to summon anybody besides Corrine. She sometimes has to be on Manual (i.e., the person player one is controlling), but that's only if she hates you like she hates me ^-__-^;;

What the heck is this T vs S thing, anyway?

T is Technical, and S is for Strike. Basically, depending on whether your character is T or S they'll learn different techs. And no, you can't learn all the techs for both sides.

How do I get this multi-player thing to work?

Set the second character you want to use into the second slot in the party order menu, then put your second controller into the second port, then go into the second character's tech menu and set them on Manual or Semi-Auto (I recommend Semi-Auto, since it'll target the nearest enemy instead of you having to run all over the screen trying to lock-on to an enemy).

What is this tech skills glitch you were talking about on the Ex Skills/Tech Skills page and why did you make me come here? DON'T YOU KNOW I HAVE BETTER THINGS TO DO THAN CLICK ON AN EXTRA LINK!?

Ummmm.... K? But you had time to write out that whole complaint? K. Anyway, it's on this page instead of both of the other two pages cause I hate repeating myself. DON'T YOU KNOW I HAVE BETTER THINGS TO DO THAN COPY-PASTE THINGS!? ... *cough* Anyway. Here is how my friend explained it to me: Some clever person figured out that if you put Lloyd in the first place in the party, set Eruption to the C-stick shortcut, took Lloyd out of the party, and made Genis forget Eruption, you could then switch Genis to S-type, learn Flame Lance, switch Genis to T-type again, and put Lloyd back in the party so that he'd still have Eruption on the C-stick shortcut. Then, in the next battle, you use Eruption until he learns Explosion. You have to do it in that first battle, though. After one battle, it disappears from Lloyd's C-stick. (Thanks to Lunar Eclipse (who is still secretive and paranoid) for the info!)