Great question.  What all this really boils down to is the polar pattern or pickup pattern of the microphone.  Some mics will pick up more sound from the front and less from the sides and rear.  Mics that are extremely directional are good for rejecting the loud drums behind you and also rejecting the sound from a PA speaker that might be right in front of you.  Many handheld mics have this type of cardioid or supercardioid pattern.  Other specialty mics have different patterns that may pick up from all around or just from the front or back.  These may be options for you, but won't be as flexible in the long run.  

Once you decide on a pickup pattern for your needs, you can start looking at the mechanics of how the mic works - condenser, dynamic, ribbon ... all that stuff.  You could stick a dynamic in front of you and your guitar and end up with a passable result.  Personally, I'd go for a large diaphragm condenser since they seem to pick up a bit more of the bass and give a nice sound in a solo context.  The range of choices is dizzying, so nail down a price range and pick one based on reviews and whatever else matters to you.  More expensive mics have higher quality components that will produce a better sound.  Audio equipment gets expensive fast and there's not much payoff over a certain level.  You also have to think about WHERE you are recording, as room acoustics can 'cheapen' your sound.

You need to have something to plug this microphone into - typically called a preamplifier or preamp.  These are built into mixers, computer audio interfaces or stand alone units.  A shure 57 or 58 can really shine with a good preamp.  If you plug it into a low quality preamp, you'll get a low signal, a noisy signal or a quiet/noisy signal - yuck.  If you have a condenser microphone, the preamp will need phantom power in order for the microphone to work.

Some other ideas for you...

Another option might be a hand held recorder which can be carted around, run off battery power and then transferred to your computer for editing and distribution.  Super easy and cheap.  And you don't need a computer with you - which is always nice.  Other options are recording with a phone using some kind of USB microphone.

I have a video demonstrating polar patterns here:  
            
                
                    
                    
                    
                    
                    
                
            

What should I look for in a recording microphone for personal use?
Things is really nice GTD (Getting Things Done) app only for Mac.

Is there something like Things for Windows?

The closest one I've found is Doit.im. But I've heard that it is unstable and its website seems outdated.
