Referral Check Protocol

This One is for the Ladies (But Men are welcome to chime in, as well): I try to be very diligent when checking referrals for potential clients and always ask for references when contacted. Thus far, I haven't had any real issues when contacting another provider to check a referral but I also don't want to bother anyone when calling either.

Is there a certain protocol that I should follow when contacting another provider to get a referral? I want to be respectful of your time as well your willingness to provide me with this information. What is the best way to contact someone when seeking a referral: email or telephone? What information should I collect from a client prior to contacting you so I'm not wasting your time or the client's time with multiple phone calls to collect the needed information? Is there a time when I should or shouldn't call so I'm not being too intrusive in your daily life, as well? And any other information or advice is of course welcome regarding this issue!!

Thank you all in advance for this information!!
email or PM would be the best and info to give would simply be:

This hobbyist gave you as a reference, his handle and then what she remembers about him, for instance, his physical looks, hair color, any facial hair? ect. and ask the hobbyist to give you something he feels she would remember him by, and then ask her that via email.
As a provider, if my phone # is posted on my showcase, website or any reviews, you may call me. But I don't post my # anywhere, so email either via eccie, my email address (if it's on my showcase, website or any reviews), or via p411 is preferrable.

Clients should not give out a provider's phone # if it isn't public information already. Email the provider. If she hasn't gotten back to you within a few hours, then let the client know she hasn't gotten back with you, and see if he would like to call or text her.

If you need any help or have any questions, feel free to ask.
I think that PMs are the best way to go unless you personally know the other provider and have contacted her before. Pretty easy for me to create a sweetcarrieXXX@youmail.com and have you contact that email address for a reference. You call it, I confirm, and then some asshole or a cop shows up at your doorstep.

If LE really wanted to bust someone, using a burn phone to generate this type of reference check would also work.

With PMs, at least the lady's real identity can be confirmed.
Good advice!!! Thanks so much....PMs is probably the best way to contact due to the LE situation..at least you know you're contacting THAT person!! I didn't think about that issue at all!! Thanks!!
I prefer for you to send me a PM with his name , handle , around the time that i visited with him (he would give you this info.)and something that i would remember him by , and his contact information.

Once you send me the PM i like for you to text me and let me know that you sent it so that i can get back with you ASAP. I do spend alot of time on here but I also work and when i do i dont check my PMs for hours at a time if im NOT looking for something to be there !