Depends just how far you are. Generally the attic is a great location as it's high up and not going to attract lightning. I had about a 4' long whip antenna from a company now gone that worked great, I think Magnum Dynalab now sells some too.
If an omni doesn't give you the gain then you'll need to go to a directional unit. Those work great but you may wish to install with a rotator.
Above all else, avoid using a signal amplifier unless you must. They tend to just amplify noise.
Another alternative, and one that worked really well for me, was a combination TV/VM antenna with the right signal splitter. Amazing FM reception when turned the right direction.