I've always been scared of adjusting my truss rod after a couple of crunchy experiences (nothing bad happened, it just sounded bad) but feeling a lot more confident after chatting it through with Charlie.

Tools

You'll need an Allen Key, 4mm is the most common, maybe a 5mm. Some instruments may be in Imperial measurements, you'll just have to try them and see.

Some newer models have a visible adjuster that can be turned easily with many tools - called Spoke Wheel - a most excellent design!

Many vintage and reissue designs take a screwdriver - and you have to remove the neck to make the adjustments! A proper pain in the ass - strings off, neck off, adjust truss rod, neck on (hopefully in the right place), strings on, test... repeat until you get it just right. Horrible!

Have a look and see before you decide to get started!

Hints

Make sure the guitar is in tune! and tune after any adjustments!
You'll almost certainly need to adjust the truss rod if you change your string gauge.
Hold down the first fret and when you make your adjustments so you don't make mistakes based on the nut height.