Being new to shooting, I am in the process of working out a grip. I have a relative who is a SWAT team commander in Farmington, NM, so I asked him to show me how he shoots a pistol, which he was glad to do.
His two hand grip is with thumbs high and parallel, so the dominant thumb is above the thumb safety and the non-dominant thumb along side or above the slide release. He holds his thumbs parallel (ie. not crossed) and extends the dominant arm then pulls in with the non-dominant arm to create kind of an isometric tension. It works fairly well. On my first day firing an H&K 45, I was able to get a decent grouping at 8 yards or so. Even so, the grip feels fairly awkward and the recoil of the pistol causes the slide release to gauge into my thumb.
Since I am new to the process, I wanted to do a little exploration. Most German guns have some ribbing placed along the front of the trigger guard. I have been firing my airsoft Sig replica with the non-dominant forefinger on the front of the trigger guard. I initiially gripped my H&K the same way and was quickly corrected. I didn't think it appropriate for a newbie to debate an experienced shooter on how to grip a pistol, but I was still wondering why all the German guns have the ribbing along the front of the trigger guard if it was such a bad idea.
Does anyone have any resources on various ways to grip a pistol? I would kind of like to explore various methods before deciding which one is right for me.