This part of the forums are for reviews. Immediately below there is a section for questions, the 411 section.
Yes, there are many scams.
That aside, the simplest way is to search this forum with the providers name and last 4 digits of phone number (ie Jenny 5309), sometimes different combinations.
If there are no reviews or mentions, asking for deposit, don't.
Some legitimate providers do ask for deposit, particularly first meeting, maybe 10 percent at a guess?
Simply spend some time reading reviews for the last 6-12 months, should give you some ideas.
If the provider, or price, or something looks too good to be true, it probably isn't.
Good luck!