Thanks for your advice everyone. I’m meeting with a new client later this week and I’ll keep your advice in mind.
I got I Draw Cars and some Gnomon Workshop DVDs for Christmas, so between that and school starting back up I should have plenty of sketching practice in the next few weeks. 
I think my problem is I take long breaks in my sketching practice so any time I spend sketching is just getting my skills back up to where they were. I just need to draw more frequently.