I usually bend the pins slightly to hold components to the board, but you may not always want to do that with ICs. If you're not using a socket, the pins will be too short, and bending them could put stress on them and possibly cause them to break. In that case, there is an adhesive putty you can buy that you can use to "stick" your IC to your board while soldering. If you are using IC sockets, and they are new, with long leads, that is really ideal. Bending the corner leads slightly will be the easiest way to temporarily hold it to the board.
As for holding the board down, you have several options. Personally, I (depending on the size of the board) use a "helping hand" tool, which is basically a heavy base with two "arms" branching off on either side. They are jointed in a few places, and on the end there's an alligator clamp. I have found this to be more than sufficient for small, lightweight boards. However, if your board is larger, I usually take a couple of pieces of corrugated cardboard and put them in my table vise, with the board between them. The cardboard protects the edges of my board from being damaged. If one layer of cardboard on each side doesn't seem like enough, go ahead and put in a second one. The point is to protect the board while holding it firmly within the vise.
Just my two cents.
Regards