I recommend tracks, I detest poles because they stand away from the window so letting heat out and light in. Particularly useless in a bedroom.

You will need holes drilled in the wall to put up a pole or track. There may be a solid lintel above a window so it is not always that easy and needs the right bit on the drill.

Make sure you have plenty of curtain hooks, the more the better to make the curtain hang right. After bitter experience, I prefer the standard curly curtain hook that goes into the header tape on the curtain and hooks into a ring on the glider on the rail. (and breathe...) The all-in-one jobs where the glider hooks directly to the curtain involves a rough piece of plastic that wrecks the header tape. I inherited some curtains with this house and these stupid things have destroyed the headers.

there are usually 3 positions on the header tape for the curtain - use the one that means the curtain covers the rail.

you can add curtain linings if needed; as well as adding insulation they make curtains hang better.