As mentioned earlier, pistols with greater muzzle flip affect accuracy only in that it creates more of a flinch in the novice shooter. When the muzzle jumps up and to the right, the shooter has a very strong subconscious urge to press down and to the left while pulling the trigger to compensate for the muzzle flip. That's why so many beginners shoot low-left. This urge to flinch must be overcome for any kind of accurate shooting, handgun or rifle. That's why .22's are such great practice. In addition to being economical, the overall lack of muzzle flip and recoil allows the shooter to concentrate more on the basic principles of shooting, namely, acquiring correct sight picture and holding it steady while causing the hammer to fall. If repeated enough, these principles will become innate enough that, no matter what caliber you're shooting, as long as you line up the sights right and don't disturb your sight picture when causing the hammer to fall, you'll hit your mark.
There are a few tricks for beginners to diagnose and weed out a flinch. For semi-autos, have a friend load a snap cap randomly in a mag. When you get to the snap cap, the flinch will be painfully obvious. A good shooter will allow the hammer to fall on the snap cap without disturbing the sight picture at all, keeping the pistol steady throughout the entire process. The same can be done with a revolver by randomly loading up less than a full cylinder. If you're flinching, it'll show on the empty chambers.
Basically, you want to line up the sights, steady yourself (control your breathing), and slowly squeeze (not pull, not jerk) the trigger until it breaks. When it breaks should not be on your mind at all, it should be a surprise. Anticipating the break will lead to flinching. Just concentrate on holding the sight picture steady. A lot of new shooters find it helpful when I tell them to pretend that every shot is a snap cap or an empty chamber, that no recoil will be felt when the hammer drops. They tend to flinch less that way.
Dry-firing is another good way to practice good shooting techniques without worrying about flinch-inducing muzzle flip and recoil. If you dry-fire and shoot .22's a lot, you should be well on your way to accurate handgun shooting.
As for your grip, it should be firm like a good handshake, but not to the point where you're squeezing the tar out of the pistol. You need your grip to be firm to allow the pistol to cycle properly and to get back on target quickly. Too firm a hold, however, will cause your muscles to tremble, then bye-bye steady sight picture. More importantly, however, your grip should be consistent from shot to shot. Consistency = accuracy, right?
Keep shooting your .22. Lots of people skip the .22 and go straight to their .40's, .45's, or more, then wonder why they can't hit anything. You have to get that whole proper shooting process programmed into the muscle memory first, eh?
Oh, yeah: Practice doesn't make perfect. PERFECT practice makes perfect.