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My colleague and I are going to (try to) paint a room (or two if we're lucky) in my new home today.

The walls are currently painted with a similar color to what I am choosing to repaint them with. They are a little dirty, which is why I am repainting them.
Before repainting, is primer required over the entire wall and ceiling or just required on areas that we will have patched due to small holes?

Thanks!

Not sure the correct way to do it, but I would personally primer coat first. Just like a car is painted in the 49 other states...primer then paint. Here, we just primer. Done.

Thanks F1Pilot.
We will also the paint store and/or Home Depot for tips.

You must primer first if you are using latex on oil or the old paint is darker,if they are both latex and the same color I wouldn't.

If you are painting over the same type of paint then primer is not really needed. You said that the walls are dirty, correct? Then, I would wash the walls then primer and then paint. To wash the walls all you need is a large wet sponge to remove all loose dirt and grime. Let dry and apply the primer. The primer will seal the walls and cover some of the imperfections and will save you on paint, because the walls will absorb less. Make sure you use a quality primer and paint. Ask your salesperson about which primer to use with the paint. If you are just looking for a quick fix then go ahead and paint (no primer/no wash). Good Luck.