Just because it's crowded does not mean at all that it isn't "Do-able". Here are my top 3 tips for getting a ton done during somewhat busy seasons:
1. Arrive early early early early. #1 tip. If you can't do anything else, do this. Get to the gates 30-45 minutes early and you will not wait in any lines for pretty much the first hour. Most people show up around 9:30-10AM so if the park opens at 8AM you can have a lot of time to enjoy short lines.
2. Use FastPass as much as possible. Hydroguy has some great threads on FP. It works very much like the WDW ones, but there are some advantages to DLR FP. For one, Grizzly River Run(DCA) and Roger Rabbit (DL) are not connected to their own park's central FP system, allowing you to obtain FPs for them even while holding onto another ride's. Also the proximity of the parks from each other makes it very easy to hop and be holding FPs for both parks at the same time.
3. Understand the attractions. Know which rides have long lines, which rides have high capacities, which rides have FP or single rider lines. You don't want to be riding Pirates at 8 in the morning because that ride has such a high capacity that you can get on with a short wait almost anytime. On the contrary, you don't want to ride Peter Pan, Dumbo or Nemo at 1 in the afternoon when their lines are 60min+. Research on the DIS and other sites, maybe buy the unofficial guide, as it's very good at this kind of tip.
Also, I recommend hopping instead of having the mentality of "one park, one day". You can escape the huge midday DL crowds by simply walking 100ft across the esplanade and going to less crowded DCA.
