1. If you haven't already purchased VIP membership to read full reviews and be able to see ratings and sort reviews by profile characteristics, do so now. The cost of one month of VIP is about a tenth of what you are likely to pay for a one-hour session with a good provider.
2. Do your research. As Betty Cocker put it a few months ago on this board, TER has an awesome "build-a-babe" feature. Decide what aspects of a lady's profile matter to you (age, race, build, services offered, piercings or lack thereof, etc), and do a search with those criteria.
3. Read the full reviews; don't just look at numerical scores.
4. Related to #2 and #3 above, be specific. If you are looking for an early 20s spinner with blonde hair and a submissive demeanor, you probably won't be as turned on by my #1 recommendation, a 44-year old Native American honey with a lot of attitude.
5. Search on Washington DC. In most listing and review services, this gives you results for the entire metro area rather than just DC proper.
6. Good and safe providers are serious about screening. P411 is a good start, but be prepared to disclose a lot of personal information in screening if you don't have other providers to vouch for you. Some won't see you anyway without references. Don't get offended; this is for your protection too. If both of you aren't careful, you might find yourself being told to address the lady you thought of SexyVixen as Officer Patterson when they put you in the squad car.
Good luck!