First-be aware that you'll still have to fill out the same paperwork when you purchase frame that you would complete gun,as that counts exactly same as buying a whole firearm. Secondly,like dillinger said-get a very detailed and complete manual with PLENTY of pictures,on building 1911 and even dvd if neccesary,study them until you almost have them memorized. Only then should you choose a complete parts kit which incluse everything but frame. There's a bewildering array of parts kits on the market,so get the best you can find,by a known maker/brand to ensure quality parts. www.brownells.com
is the company which I've dealt with for years.
You'll also need a few basic tools-that's where the manual/book/dvd will help you. A prime example is plunger tube-try to choose frame with plunger tube already staked in as I've had several people walk in my shop wanting this done as they,as beginners,found this step too difficult to do themselves. You'll need the exact tool to stake plunger tube.
Another consideration is fit. Hand precision fitting is best left to professional gunsmith,armourer,or someone inimately familiar with building/fitting 1911s. Yes,it will shoot just fine without hand fitting/adjusting to eliminate tolerances,but you'll never acchive the level of accuracy it's capable of.
Also,choose the parts kit which include the exact type of parts you 'll want such as which grips,grip safety,safety,slide stop,sights,etc so that you won't have to buy certain parts twice in order to get exactly what you want.
I'm not trying to scare you or add confusion,just attempting to help you make intelligent choices in order to wind up with THE exact pistol you want,in addition to spending extra money for parts you'll never use. Any questions or advise you need along the way,we'll be delighted to help. I'm SURE I missed a lot of points in trying to be generalized so other people can help pitch in. We all have our own preferences on brand/type/model/parts so I'll not get into that part as almost all my customers want different things.