The German adverb mal is one of those highly useful, largely untranslatable words that foreigners can’t get right. Das Mal means time, and mal also has to do with time–it even means “times,” as in drei mal drei, three times three.
But when mal comes along with an imperative verb in a sentence, it’s often there to reduce what would be a stern command to a gentle suggestion. So, for instance, schreib mir (write me) might sound forceful, but schreib mir mal just means “drop me a line.” Sag (Say) and Gib (Give) are pretty abrupt orders and the sort of thing a small child might say, but Sag mal and Gib mal sound more acceptable–although these are all, of course, statements to good friends.
If you put mal in front of an infinitive, you once again create a gentle suggestion: “Let’s …” So, mal probieren — let’s give it a try. Or mal sehen — let’s see.