Here are some general tips for you:
1. Start off very slow (set a base amount of domains you will register per month)
2. Register only .coms - .net if keyword is awesome
3. Focus on keywords with high traffic (see Google Adwords Keyword Tool + hit exact)
4. buy domains that flow well and sound "right"
5. buy keywords that have high potential to make money (cell phones, lawyers, big tickets g+s)
6. Don't expect to sell anything
7. Develop the sites so you can hopefully have the domains pay for themselves
8. Make a for sale sticker for the website. Slap it on there so an interested person knows you are selling.
9. Ask for constant criticism for your domain buying. You'll soon find out if you're doing well or not.
10. Chart all of your domains with details in an excel spreadsheet.
Remember that you are in a for profit investment. Its a small business operation. Set out goals and be honest with yourself on how you are progressing.