I am going to be finishing my basement. Is it best to place new heating vents in the ceiling or run the line down the wall to near the floor. I understand I will need to run a cold air return should this be at floor level.

Whatever is the easiest to do. A basement is a restricted type of area that in many cases depending upon the way it was constructed will determine which type of vents you will be able to use. Now with that said I would prefer to have my vents discharge at the floor which means the heat return will have to be high on a wall in the space. If you do this you can Pan in a floor joist area and use it as a return air.

Remember the basement is naturally cooler than the rest of the house but it also usually has the most moisture. I would have someone professionally do the duct layout but if that is not affordable make sure you put a assessable damper for each run of duct so you can adjust the flow of air to suit your needs.