Blender, kHed, and 3DS Max are all good. Modeling in general is something you can't just learn overnight, you're going to need to practice it to get good. If you have no prior modeling experience I recommend Blender as it's really popular, free and has plugins for source. kHed is also free and is easy to use but has no tutorials at all on it so unless you want to try and figure it out yourself I don't recommend it (if you do figure it out though it's awesome for making small minor props). 3DS Max is good but costs money.

Compiling models is also tricky for those new to it so don't be surprised if your model doesn't compile in the first try.