Disclaimer: This list is not complete but will be an ongoing process. As the hobby changes, so will this list. New tools will be added when possible. Feel free to ad your own tools for the benefit of us all.
I've been a hobbyist for the last 15 years now. I remember my first entertainer in Dallas. She was like 17 years older than me and turned me out. She was my ATF and I actually knew her family after seeing her for so long. I was lucky with her. Then, I ran into a couple of nut jobs out there that actually stalked me. I actually moved to get away from one. Now having said that, let's get into this list.
1) Tineye.com -> Before you even call up an entertainer, you can check and see if it's a fake picture. If it is, it's a good sign of something fishy and you should stay away.
2) Google Voice - You never want to give out your real phone number. You don't want to get caught in a bad situation. You can set google voice to ring your regular phone at certain times or have it completely turned off. If you have an android phone, you're in an even better position since the app for android is full of features that you would normally have to use on your desktop.
2.5) Throw Away Gmail Acct -> I put this as 2.5 since you have to have a gmail account in order to get a google voice account. Create a totally new gmail account and don't use your private one. The old lady might run up on it.
3) A hobby car. - I have a hobby car that I use to see new ladies. Can't take the risk of my regular vehicle being seen at a naughty place. A little $500 car that you keep in your garage will suffice. It doesn't have to be anything fancy. You're not going to impress.
4) Condoms - This seems obvious but I've noticed a lot of hobbyist out there who like the NCFS. That's crazy son! You need to keep it healthy.
5) Ginseng - You gotta keep a few bottles of ginseng around. You don't want to end up in the ladies forum with the rep of being unable to get it up.
6) Mouthwash - For those of you who are into DFK, just think about how many sessions of fellatio uncovered she's had before you. If you're going to do it, wash your mouth out ASAP. Plus, you don't want to go see her with funk mouth.
So, if you have any other tools that you use, please add them to the list.