Ya I've been trying to figure out whether trinity is worth it, but the increased slow and sheen affects are very helpful, as well as the movement speed increase, which helps with alistars low starting speed. I tried going hp early game, but getting a warmogs for a third item often led to minor mana problems, vs. getting the 300 extra from trinity. Suggestions on order of the items (maybe frozen heart before trinity, or something like that) would be appreciated, but don't forget to leave your reasoning. Thanks :).

I might recommend that you get warmog's armor after your boots to give you more staying power. This is more of a general thought as I am not well versed with alistar.

Feel free to comment changes, but I would appreciate explanation on them. I hope to get some great ideas, and hopefully someone can help me write an explanation on how to play, rather than jsut providing a build.