I brew on a RIMS system - Brew-Magic. Here's my procedure.
In the Mash Tun, I move my inlet tube to rest right at the false bottom. I then pump over just enough hot water to cover the false bottom about 1/4 inch. Then I add in all of my milled grain (I run a 3-roller mill at about 0.4 inches with fairly complete husks and very little flour). Next, I very gently pump over until I hit my required mash volume. This has the effect of hydrating the malt from the bottom and pushing up all of the air trapped in the grains. I'll do a very short and gentle stir, just to make sure no dough balls have formed (usually do not with this method), and then move my inlet tube to rest about an inch below the mash level. Lid on.
I set a timer for 10 minutes, and setup the valves to recirculate. After ten minutes, I start to pump very slowly. Every 5 or so minutes I increase the circulation rate but seldom go above about 75% of my throttle valve's fully open state. Circulation continues through any steps or mash out. I gravity feed the wort to the kettle, reset the valve configuration for lautering and do a slow sparge (valve never gets above 25% open) for about 45-50 minutes.
If my mash is floating up, air is getting under it and my valves are setup wrong. If I circulate right after grain in - I risk compacting the mash and sticking it, as well as getting excessive flour and other bits into the pump. By letting the mash rest and more fully hydrate, I get consistent results.