what are the most commonly used features in solidworks to model a bicycle frame and what is the best starting point?
I would start with a 2d sketch of a bycicle from the side. For complicated sketches I use draftsight. You could search for a bike on the internet, copy it into draftsight and then draw lines over it. Thats your bike sketch.
Then in Solidworks you insert the drawing (note: you have to save the draftsight drawing as an older version than solidworks, otherwise SW can't open it. Once you loaded your Draftsight drawing, it's better to explode the sketch block.) Or you use your SW sketch to model your bike.
Now comes the moddeling: I would make a perpendicular plane at the end of every line. On those planes you draw the section of the frame (Circles, most of the time). Then you can use different features like: extruded boss for straight frameparts; Sweep for not straight frameparts and loft for fluid shapes.