I ride alone.
I like to just go out and do it and I live so close to great trails that waiting for a friend to drive/ride over just kills me. I do ride with people every now and then but usually i'm faster than them and I know the trails much better so I don't get caught up in the technical (though not hard once you know it) parts. However, I like to ocasionally ride with people that are great because they definately help to push you and if you have any questions about how to do something they'll help.
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practice, practice, practice...
Last trail to kick my ass: Eagle's tail