If someone can't trust you enough without getting a call/text from them; then they are to needy for me.
Don't over do it. Don't respond to a text right away either, but don't wait an hour/s
Depends on the personality of the relationship.
My boyfriend and I message each other everyday through skype, but only talk to each other one the phone once a week.
How ever often is mutually agreeable between the two of you.
As much as you want dammit! lol J/K!!!
Go easy with it. unless he/she is wanting to banter back and forth. THen have fun with it.
Whenever it feels right for you.