With a full rig (main / genoa) the boat should be balanced, personally I like a little bit of feel on the tiller – so a tiny amount of weather helm.
The boat should be sailed flat – once you start heeling then the pressure of water against the leeward chine will increase the weather helm – so ease the mainsheet if you have run out of crew weight. Heeling is likely to be the main cause of weather helm – as I say, ease the main and sail it flat, you will go faster.
If you are (cruising) under reduced sail you have to balance a reduced mainsail with a smaller headsail (jib rather than genoa).
And of couse if you happened to be sailing a Wayfarer with a jib and full main that would give a lot of weather helm.