If you have a Mil Spec to start from, look into a bbl bushing you can hand fit. Also a trigger that you can adjust the take up but also hand fit to the frame. Drop in triggers can be better than the one in there but you can end up wit that little up and down wiggle that you will not be able to get out. A nive beaver tail safety and ambi thumb safety can do wonders especially if you're "wrong handed" like me
Understand that fitting parts is a bit tricky. You are going to be trying to hand fit the parts to the weapon. This will take a good set of stones and maybe a decent set of jewelers files. Though I do not recommend the files as much as it's easy to remove too much material. It takes a while taking off tiny amounts of material, trying to fit the part, then trying more if it does not work. The stones can help a great deal working internals to get that break like class trigger that just makes me feel all warm and fuzzy as I sling lead down range.
You will want to do some research before trying this. Clarke Customs, among a few others have great DVDs on how to hand fit 1911 parts for best results. There are several pretty good books and DVDs on this subject though. I think Midway has them. Brownells might too if I remember right. If I remember right the Clarke one even shows how to fit the slide to the frame a little better to help a bit with accuracy too.
Just remember, it takes time and a steady hand to do this kind of stuff but it is a lot of fun really. I did a few things to my old Mil-Spec and it's a much better pistol that it was. It freaks some people out when you whip out one of those Mil Specs and group what many higher dollar pistols do.
Edit to add: As NGIB said you will need some jigs. This can save you a lot of pain, heartache, and money.