common sense: if you need a ride, call for one.
not common sense but should be: if you call for a ride, call ONLY once you've secured ready position. so, if you want a ride, and you want to be picked up at 6 (possibly at a spot), you damn well be at that spot at 6. if there's a chance - even the slightest chance - that you will not be at that spot at 6, then don't call until you've arrived at that spot. it stinks for you, since you want to be picked up precisely at 6, but this is a sacrifice you'll have to make. the person picking you up should not have to wait on you since they are ultimately doing YOU the favor.
real-life example: "hi, my plane just landed, come pick me up in 15 minutes!" umm, sorry, how about i come pick you up once you've made it through baggage claim and are at passenger pickup, that way i'm not stuck waiting an hour while your bags are slow getting off the plane.