Until Ive met the person at least once. Reason being is, I dont like calls/texts in the middle of the night especially from strangers. Also, I find its easier to screen with email. Once Ive met a person, they are free to call/text during the day anytime If Im not busy, I'll happily answer them

For Me...

Personally I like the private messaging system (pm) as I like members who can be easily checked out. For screening purposes, I prefer emails from non-members. Calls/texts are good as long as I have been initially contacted by one of the previously mentioned methods first.

Phone only-limited or no internet access, or does not have time to answer emails. Might prefer to hear voice as a part of screening. Can facilitate meetings faster vs. back and forth of email/text.

Email only-might have limited ability to answer calls and talk freely. Some people are nervous talking on the phone, and find email conversations easier to communicate.  Can avoid being put on the spot to discuss services.  Prefers advance planning, and weeds out guys looking for "right now" appointments.  

Texts (prefers)-combines quick facilitation without need to worry about taking calls/who might be around to overhear.  Also cheaper way for some to communicate if they still have pay-as-you-go minute plans on phone but unlimited texts.

Texts (no allowed)-don't have time to constantly be texting with clients, especially those trying to sext, asking for pics, etc. Text messaging not discreet-logs kept by phone companies that can be later pulled and used in court, or found by significant other if phone is accessible to them and not locked.  

These are some basics...bottom line: everyone has difference preferences and comfort levels on communications.