You can do that once you figure out who your angels and guides are. Then you know what their "voice" or their "style" is like.
Until then, there remains the possibility that you can encounter beings that pretend to be benevolent but aren't, or seem malevolent but are there for a good reason.
As I said: you can mark a circle, decide that your space is safe, pray a bit, otherwise begin with a set intention.
It's like saying, "I won't date anyone that I'm not going to marry." But you usually find out if you're going to marry them by dating. Sometimes you date a heartbreaker instead of a spouse. That can happen. Some people marry their friend since childhood, just like some people just know who their guardian angel is their whole life. That's great, but it's rare.
If you're a beginner at channelling messages, it's not unusual that you'll get some junk first.