Don't forget that miles expire. So, if you want to keep your miles alive, check the expiration dates and plan a way to keep them alive. (IIRC, Delta doesn't expire.) Any use in or out will generally work.

As mleyd said, get a plan and work it. Where do you want to go? What is the best way (in terms of miles) to get there. Don't forget that Chase (and maybe Amex, but I don't know for sure) will transfer to hotels.

I'm chasing status on airlines, so I'm using points mostly for hotels. But there, you also have to plan and know the value of the points. I'm desperately collecting HHonors points for a vacation in the Seychelles, but I was on a trip to Oman and rooms at the Hilton were $200 a night but only 5k points. So I burned my points because it was a huge benefit.

I am kicking myself for not using Chase points to book Iceland Air for a trip I'm taking this week. I don't think Chase points for air is great (transferring to United is generally a better deal) but I could have gone for free and wound up paying $1300 for air. Oh well. That's how you learn.

Read flyer talk. Read all the threads (if time is important, skip Omni). But have a plan or at least an idea.