Looks like lipjerk probably found you a good link for the information you are looking for.

The most important thing is that you know a few of the basic properties/characteristics of each type of line. There are three primary types of line we use in bass fishing. Here's my short version:
Braid: No stretch, high visibility, thin diameter, low memory, floats, high abrasion resistance.
Fluorocarbon: Very little stretch, low visibility, medium memory, sinks, good abrasion resistance.
Monofilament: High stretch, moderate visibility, high memory, floats, lower abrasion resistance.

These are very important properties to consider when selecting which line to use with certain presentations. Out of those characteristics, this is how I would rate those characteristics in order of importance when considering which one to use... starting with the most important characteristic...
1) Floats vs Sinks (buoyancy)
2) Stretch
3) Abrasion resistance
4) Diameter
5) Memory
6) Visibility

As you can see, visibility rates pretty low on my list. Other characteristics are far more important because most of them will affect the performance of your lure which impacts how many bites you will get far more than line visibility ever will. These characteristics are important to consider because, for example, if you throw a topwater lure on fluorocarbon line, which sinks, it will bog the lure down in the water and screw up the intended action of the lure.

To answer your questions specifically:
-With braid, sometimes I use a leader and sometimes I don't. The main things I consider with tying on a leader to braid are... what lure/presentation am I using, what is the water clarity like, and how heavy of cover am I fishing around?
-When I use a leader with braid, it is pretty much always fluoro. Except for when I am tying a Carolina-rig, then it's mono.
-A good, all around line? Fluorocarbon is on probably 70% of my reels, so I'd say that's the best bet for all around. If you've grown up using mono though, beware that there is a learning curve when using fluoro. A lot of guys hate fluoro when they first start using it. It has very little stretch and can cause more tangles/backlashes when you are first using it. A lot of guys give up on fluoro after one or two uses and call it "[censored]," but that's because they never get past the learning curve. Get past the learning curve and it is much better than mono.

Hope that helps.