What Warners/New Line/DC can learn from Marvel's films, as well as from past DC films:
1. Hire great directors.
2. Make sure the great directors you've hired stay on the right track in terms of a cinematic vision that best serves the characters.
3. When you have a great director with the right vision, do everything possible to have him stick around and at least complete a trilogy in those cases where the character should be featured in a series. Which brings me to...
4. Not every character needs to be franchised. Sometimes it's preferable to just make one great standalone film and leave it at that.
5. Following on from the last point, rather than make lots of sequels, lay out a game plan whereby you make DC films that exist in the same universe and have repeat appearances by characters, yet stay fresh and different by putting characters onscreen in various combinations. For example you could make a Green Arrow film that features Black Canary as well as GA, then a Catwoman film, and then a Birds of Prey film introducing Huntress and featuring repeat appearances by Catwoman and Black Canary.
6. Don't settle into a rut whereby there's a standard superhero story template that is applied to almost every film. Mix it up with different styles of storytelling, essentially different genres. Make Catwoman as a sexy heist film, Plastic Man as a riotous comedy, Green Lantern as a science fiction epic, etc.
7. Spend your money wisely and pick the right release dates. Not every superhero film needs a massive budget. For those characters who don't have spectacular, budget-busting powers, make films with modest budgets and release them in the spring. When you spend a lot of money on those characters who lend themselves to summer or Christmas blockbusters, make sure you've got the right mix of elements, especially in terms of large-scale action set pieces, that will satisfy audiences and keep the box office registers ringing. Moreover, if you spend a truly huge amount of money, like $ 200 million, you have to make the film appealing to kids. An older demographic can't be relied on to buy enough tickets to justify a budget of that level.