Okay... so I play in a regular d&d 3.5 group with some friends.
Earlier we have been playing some high powered games, with fun rp and lots of hack and slash.... and a cleric that could do nothing but heal all fight, cause we just run in and bash, no thoughts no tactics no nothing.

This time we decided to do a low magic campaign, though we havent decided exactly what that means

We run shifting dm's meaning i run a plot, then the next person takes over.
The dm decides whether to run his toon as a npc or send him off on another errand.

Currently the group is at 2nd level
Rogue styled as a ninja dual wielding short swords
Fighter styled as a samurai with a bastard sword
Fighter with shield and monkey gripping large bastard sword
Scout/ranger with a bow
A cleric that once again seems to be a healing battery more than anything
And then me.....

Now i want to do something different than your standard fighter damage dealer.
Been thinking about a trip expert with a spiked chain, Hold the Line feat and Defensive Throw feat.
Also thought about the warblade from Tome of Battle i think it is, with some weapon and shield
Lastly I'm kind of settling on the warblade with shield, monkey gripping spiked chain, using hold the line and improved trip feat.

After this wall of text, a few questions:
Is it possible to make a Trip as part of a regular attack of opportunity (f.ex. on a person moving through a threatened square) ?
Any other suggestions for a better tactical melee weapon than the spiked chain (no home made weapons please) ?
Would it be beneficial to go mix warblade / fighter to get some feats and special stuff or just go full one of the classes, and which then ?
Can i incorporate one of the special attacks a warblade gets, requiring single action, in a full attack ?
Any other suggestions (apart from convincing the rest of the group to go more tactical than making sure we flank) ?

Thanks for good advice in advance