During my very first time through the game, I remember my Squall being at level 13 when I fought Abbadon at Great Salt Lake right before I got into Esthar - and that was the highest level of any of my party members. I think Quistis was at level 8. The game gives you no incentive, nor opportunity to stop and level up at all, because you never feel like your party is weak when your enemies' levels are adjusted according to that of your party. After I fought and lost for Adel for the 20th-odd time, I kicked myself and realised I needed to go back to my roots and fight a strategical battle, instead of overpowering my enemies, which is a style I've been using primarily for most of the RPGs I've played in the last few years. I think the average level of my party during the Adel fight was around 19 or 20, and it didn't help that I didn't know anything about the Junction system, but I'm glad I was in the position because it was great defeating her with my party in such a state - it was a sense of acomplishment that I haven't felt in any RPG boss battle for a while now.

After the first playthrough, I established many points during the game to stop and develop my characters, and after that first time I usually have level 40 characters before the first disk is over. I've learned a few tricks.

Examples:

I start levelling up as soon as I get access to the Training area at Balamb Garden. I fight T-Rexaurs and max out on Quake spells to junction to my STR state, until I get to the general vicinity of Deling City, where I draw Tornado from the birds the name of which presently escapes me, and junction Quake to something else.

As soon as I get Siren, I teach her L-MOD RF (after Boost of course), and buy a bunch of tents - I max my SeeD rank as soon as I become a SeeD - and mod them into 100 Curagas for everyone to junction to their HP. Instant 2000-3000 HP for all applicable party members.

I also usually have atleast the third weapon for all my main party members, though its not a priority, considering Squall is the only character who really benefits from the upgrades.