1. Learn about splicing -
The shaft and the butt are spliced in two ways:
a) Machine spliced - you can tell this by the distinctive pointed splices in the butt wood
b) Hand spliced - This has a more fluid splicing pattern and the tops of the butt wood are rounded into the shaft material.
2. Look for Matching grain
When you buy a snooker cue you get a better consistency of wood and therefore feel through the hit with a shaft and butt that use the same piece of wood throughout. Check to see that the grain matches across the joint. If it doesn't then it is generally a different piece of wood.
3. Looks don't equal feel.
If a cue looks nice it doesn't necessarily mean that it will play nice. I have had a customer recently spend £180+ on a snooker cue that looks gorgeous but he could just not get on with it. Try a few before you buy.