I was going to post a thread about the SeeD test answers, but from my experience a lot of players have trouble understanding the junctioning system. It is pretty complicated, but once you get the gist of things it is really easy to follow. I'll try my best in explaining it, but if there's anything I have missed or you still don't understand, please comment.
Junction - Guardian Forces
GF junctioning is straightforward, so why am I tutorial-ing this part? Well, whichever GF you junction has an impact on what sort of magic you should junction for each character. For example, if you junction Quetzacotl you'll need lightning based magic. Also, be mindful of which GFs and how many you are junctioning to characters. There's no need to give your party evenly distributed GFs if they both have HP-J abilities. Take a look at your GF abilities and sort them to your party.
Junction - Magic
At the start you need to junction magic that suits your GF's element. For example, if you junctioned Diablos to Rinoa, you are better off junctioning Demi to her for an extra boost. Below is a list of magic you are better off junctioning then the list of the ultimate junctions.
Aero: Luck
Apocolypse: HP/STR/VIT/MAG/SPR
Double: HIT
Flare: HP/STR
Full-Life: HP
Meteor: MAG
Pain: MAG/LUCK
Quake: HP/STR
Reflect: HP/SPR
Thundaga: HP
Tornado: HP/EVA
Ultima: HP/STR
You need to aim for:
HP - Full-Life : LG Mag-RF. Refine Regen Rings or Pheonix Spirit. You can find at draw points at the Island closest to Heaven/Hell.
STR - Ultima : Forbid Mag-RF. Refine Pulse Ammo, Ultima Stone, Energy Crystal, Dark Matter. You can find at draw points at the Island closest to Heaven/Hell.
VIT- Meltdown : Supt Mag-RF. Refine Mystery Fluid. Draw from Trabia in Bika Snowfalls.
MAG - Meteor: Forbid Mag-RF. Refine Meteor Stone or Star Fragment. Draw points found the Island closest to Hell.
SPR - Curaga : L Mag-RF. Refine Wizard Stone, Whisper, Healing Mail, Healing Ring, Tent, or Cottage. Draw from Caterchipillar in Balamb Accauld Plains or Mesmerise in Trabia Bika Snowfalls.
SPD - Triple : Time Mag-RF. Refine Rocket Engine, Samantha Soul or Three Stars. Draw from Grendel, refine Double to Trible using Hi-Mag-RF and draw points at the Island closest to Heaven/Hell.
EVA - Tornado : T Mag-RF. Refine Tornado. Draw from Thrustaveis in the Great Plains of Galbadia
HIT - Double : Time Mag-RF. Refine Dragon Fin. Draw from Grendel in the Island Closest to Hell.
Luck - Aura : Supt Mag-RF. Refine Fury Fragment. Draw from Blue Dragon in Trabia Winter Island. Draw from Island closest to Heaven/Hell.
I hope this guide helps you all. If you need anything else, don't hesitate to ask.