I like to head up to Paleto Bay, get a loaded semi (cluckin bell van trailers are the best) and drive back down the GOH and drive fast thru the city, preferably past other players who I imagine go 'whoah, duude'.
Also I like to show up to missions in terrible cars like the Dilletante and convince other players they should ride to the destination with me, in my dilletante or premier or emperor. Those last two aren't terrible, just slow.
I like to try and find the most wrongly matched clothes and wear them - like boots, sport shorts, tucked in shirt and cowboy hat. and elvis shaeds. and a moustache. that weirds people out.