My husband and I used to do this thing where we'd go to the gym and just head straight to the routes that we couldn't finish from the week before. But this tended to (a) tire us out very fast, and (b) increase the chance of sprained whatevers due to lack of warmup. And then we noticed that the experienced people at the gym generally started on the very easy routes as a warmup and worked their way around to the hard routes. So this week we tried that, and it worked a treat! We didn't tire out on the easy routes (as I'd thought), we climbed for much longer overall, and I still finished two routes that I'd had trouble on last week. Success!