Showing up and watching a local match is the best thing to do.
For most types of events, you need:
* A practical pistol - if you've already got one, thats great. Otherwise, show up at a match and see what everyone else is shooting.
* 3-4 magazines (3 for IDPA, 4 or more for IPSC)
* At least one double magazine holster
* an OWB or IWB gun holster that holds the gun securely. The nylon ones aren't ideal, but some clubs will let you use them when you're getting started.
* And 150 rounds of ammo or so.
If you've got all that, then show up ready to shoot. Otherwise, show up and spectate a match. People are usually thrilled to talk about their hobbies with new people.