I recommend Susan's "lotion making thingie" as a fun, interesting intro:
http://dl.dropbox.com/u/1020026/introductiontolotionmakingthingie.pdf
The "all in one" emulsifier systems that many people use are BTMS, Conditioning Emulsifier, Polawax, and Emulsifying Wax (aka e-wax or e-wax NF).
BTMS and Conditioning Emulsifier are very roughly similar, except BTMS is a brand name product from Incroquat and conditioning emulsifier is a generic version. BTMS comes in several flavors -- BTMS 50, BTMS 25, BTMS 225. Susan recommends BTMS 50, but it's hard for me to find it -- the stuff I have is basically the generic version of BTMS 25. These emulsifiers are cationic, meaning they have an electrical charge. This makes the product adsorbent, meaning it will "stick" to skin and hair longer than a non-ionic (not electrically charged) emulsifier.
Polawax, and Emulsifying Wax are also roughly similar products, except Polawax is a name-brand version from Croda and e-wax is the generic. These emulsifiers are non-ionic, meaning they do not have an electrical charge.
The generics can vary somewhat by manufacturer, whereas the name-brand products are consistent. If you use generics (as I do) and get good results with one supplier's products, it might be good to stick with that supplier to get consistent results.
http://swiftcraftymonkey.blogspot.com/2009/10/emulsifying-systems-e-wax-polawax-and.html
http://swiftcraftymonkey.blogspot.com/2012/08/why-did-i-buy-that-rita-btms-225.html
You can create your own emulsifier system by using the HLB method, but I'm not really sure it's worth the trouble for most hobby lotion makers. More about HLB:
http://swiftcraftymonkey.blogspot.com/p/hlb-system.html
In addition to an emulsifier system, many people also include thickeners in their lotions. Butters, cetyl alcohol, cetearyl alcohol, stearic acid, etc. can all act as thickeners in a product. They work with an emulsifier system, but cannot replace the emulsifier. Non-butter products add thickness and texture without adding greasiness, so you can use these thickeners to make a lighter feeling, non-greasy lotion or cream if that is your goal.
http://swiftcraftymonkey.blogspot.com/2010/10/asidecetearyl-alcohol.html
http://swiftcraftymonkey.blogspot.com/2009/07/better-crafting-through-chemistry-cetyl.html
http://swiftcraftymonkey.blogspot.com/2009/07/better-crafting-through-chemistry.html