Here are some guides, strategies, and tips and tricks that will help you get past some points in the game. Please take note that these guides are not complete walkthroughs for Final Fantasy VIII. If you want those, try GameFAQs. Also take note that guides here only tackle situations where Rinoa is present or where Rinoa will benefit the most.
RINOA AND ADEL
At the start of disk 4, you'll have a boss battle with Adel while Rinoa is junctioned with her. This battle is pretty easy if you know what you're doing. This strategy I present here is the one that I usually do when I battle with Adel.
Description: Esthar's ruler before Laguna and company confined her. Released by Ultimecia, and regaining strength.
Attacks: Drain (usually used on Rinoa), Meteor, Energy Bomber, Swipe
Draw: Firaga, Thundaga, Blizzaga
Mug: (1) Samantha's Soul
Drop: (1) Samantha's Soul
Adel Stat Table
Description: Rinoa being junctioned by Adel. Immobile, because Adel is absorbing her powers. Can be released by defeating Adel.
Draw: Esuna, Dispel, Regen
Mug: (8) Megalixirs
Rinoa Stat Table
One thing to keep in mind is that you shouldn't kill Rinoa. Once Rinoa's killed, it's game over. So concentrate your attacks only and only on Adel. Avoid using GF's and Squall's Limit Breaks since usually his limits attack all enemies and in this case, it would also attack Rinoa.
It's a good idea to start of by casting Regen and Shell on Rinoa in order to protect her from the Drain spell of Adel. Next if you have Meltdown, cast it on Adel to lower her VIT to 0. Now after that just designate one healer on the group and let the other two attack Adel. Always remember to keep on healing Rinoa from time to time. If she says "Ahhhh..!", that means that she has way too low HP, so immediately heal her with Curaga if you have some. Also don't forget to re-cast Shell on her when her Shell runs out.
Don't forget, you can mug Rinoa to get the 8 Megalixirs which is pretty useful.