You need a good accurate pointing device.   You must be confortable with it.

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Some are content with a regular mouse.  Personally I cannot deal with a moving rodent so I use a trackball for several reasons.  The first one is that I do not need any space on my desk.  The second is that it is more precise and stable than a mouse.  Remember that is is a preference here, not a rule.  You should always select what works best for you.

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Another pointing device you should consider seriously is a tablet with a pen.  There are numerous brands out there so I will not name any.  What I will recommend are the features you should look at:

• Size of the tablet.  Bigger is not better.  A small tablet is often more ergonomic than a large one
• Precision in line per inch, the more the better (precision)
• Pressure sensitivity (Allows the pen to regulate the opacity and width of your changes)
• Programmable pen (Helps with reducing the keyboard use)

The drawback of a tablet is that one needs to change the way of working.  If you use a mouse or trackball you look at the screen and use your hand to move the cursor up or down.  When dealing with a tablet the cursor appears and disappears relative to its position on the tablet.  That can be disconcerting.  The result is that we have a tendency to look at the tablet to locate the pen and it's relative position...  Many folks give up on pen and tablets due to this, I very nearly did.