I've tried using my fianceé's tablet a few times, but find it difficult looking at the screen instead of my hand as I'm working.
Does anyone have any tips for becoming more comfortable so I can make better use of the tool?
Unplug your mouse for a few days. Trust me it works :) It can be a pain at first, but you'd be surprised how fast you get used to it. Of course getting good with it at illustration/drawing takes a bit longer.
Also, make sure you download the latest driver from the tablet manufacturer as it may contain support for a lot of software on your OS.
Open up Photoshop/Gimp, pick a tiny brush and start drawing. Pick something complicated that has a lot of details and just start drawing. Before anything, you need to get comfortable to not looking at your hand, you need to learn to use it with at least a little precision without thinking about it.
Trying to draw something is probably the best way to practice the coordination. You can also pick something geometrical, like a house, which will teach you to draw a straight line. Actually learning to draw a straight line in any direction is very hard.
When I got my tablet, I also did this excercise, where you pick one direction, and you keep drawing one line over another, trying for them to be as close to each other as possible.
The end result will look something like this. After a while, try doing so in another direction, until you're comfortable drawing in every direction. The movement should not come from your wrist.
Your experience may also rely on how you got familiar with analogue pen-work.
When I faced the problem, pretty much of my trouble was based on my working position and the will to get fast results with all these smarty setup. In the past I worked alot with pens, drew out of the wrist crooked over the desk.
Tweak driver software & buttons for your needs. Get familiar with the shortcuts under the hood of your software and tablet. If you don't like it, edit them!
Tablets buttons memory Remember the shortcuts and underlying functions, so that you can fully concentrate on your artcraft.
Tune Photoshop There are several color wheels out there, that proof more methods to implement color theory and contrasts in your work than the photoshop HSB-Slider.
Hold your position. Try to sit straight, not on the edge of your chair.
Hold your wrist. Move your arm not your wrist.
Use your shoulder. When your shoulder is engaged you're doing it right.
Ground your feet.: Your results are as stable as your working position. Have a good foundation.
Keep calm.: When you try to bring down a line your concentration will be tensed mostly in the middle of the trace. Don't get in a hurry. Slow, but steady lines will bring the clearest result.
Minimize distractions. Your results will improve if you turn off the music and other disctractions.
Just draw - train hand-brain-coordination with analouge material:
If you look for more:
Scott Robertsons "How to Draw"-book is a good source for improving linework.
CTRLpaint.com has a free library for getting more comfortable with software and techniques
LevelUp is a community engaged in sharing free professional knowledge about the topic http://www.fusroda.com/