Welcome to FOG and you made a great decision on the 500Q. It's a great tool.
1- The biggest challenge I had early on was plunge speed and how to hold the tool. I'd suggest you place the bulk of your weight on the front handle when plunging into an edge. Clamping your piece to the table will help with stability. Then lightly grip the back of the tool near the plug and slowly plunge in. Front holds it steady and the rear is a light push.
2- One other thing to take note of - dominos and potential blow-out by forgetting to change the depth setting. A 40mm domino, for example will join 3/4" material at right angles. But you'll want to plunge into the horizontal piece at 15mm and the vertical piece at 25mm. Just be aware of this when doing the work. I've made the mistake of not resetting the depth and cut through the horizontal piece.
3- Your Domino should have come with an accessory base that is excellent for providing stability when you are plunging down into a piece. Screw it on and you are far more likely to have a plunge that is square to the face of a piece.
4- On either side of the Domino, you'll notice a horizontal ledge that is 10mm up from the bottom. That is the center point of the bit. It will help when you want to do a row of Dominos across the face of a piece that are aligned to a line, as in a center upright on a cabinet.
5- I find that my Dominos need lightly sanding to make them easier to put in the slots. You can also put them in a bowl in the microwave and that will also remove moisture from them making them easier to insert and remove
6- some users will drill a hole in a couple of dominos that are sanded for dry assembly. The hole identifies them as dry assembly units but also lets you drop a screwdriver into them to easily pull them out if you find they are stuck from humidity expanding them
7- rule of thumb is the domino should be about 1/3 the size of the piece you are connecting in width. So on 20mm ply a 6mm domino is sufficient.
8- many will do a tight joint on the first domino across a piece. Then the others you can open up the slots for easier assembly. I usually do tight dominos across one piece and then one tight one on the mating piece on the 'show' edge and the balance as loose ones to ease assembly. You adjust mortise width with the rotating switch, BTW. Do this WITH the Domino running so the gears mesh easily.
9- definitely download Rick Christopherson's Domino supplemental manual. Lots of good info in it. You can find it here -
http://www.waterfront-woods.com/festool/
10- You will want to use dust collection. The domino is one of those tools that will cut inaccurately if chips are not evacuated from the mortise as it's cut.
Enjoy your new tool! Please share photos as your projects progress or feel free to ask questions. Plenty of help here.
neil