I realize the corpse is not yet cold (or technically even a corpse), but before GS winds down it seems to me worthwhile to start cataloguing what this year's promo teaches about next year. Here are my preliminary thoughts:

1. Start early with retail partners. This year, several merchants switched things up in the middle of the GS period to make it harder/more costly to earn hits. In particular, after the Grand Slam was in full swing
   • Biscoff raised the prices on Anna's Cookies & Biscoff spread (and in the process, changed the offer terms to eliminate the base 250 miles)
   • Vinesse jacked up prices (apron, wine chiller) and removed other cheap items entirely
   • A certain no-cost financial institution hit -- one that had been good in prior years -- went away mid-GS thanks to the foolish decision by certain bloggers to trumpet it.
   • SkyMall did double back-flips to hide or de-list cheap items; and
   • 1-800-Flowers seemed to clamp down on giving miles for any sale items
   If you did these hits early, you probably saved yourself some money and/or scored a few extra miles.
2. For e-miles & e-rewards, start really early. Don't wait until the start of GS to work on these. They're a lot less painful if you pace yourself by accruing points all year long, or at least starting some months in advance of GS -- say, by Memorial Day.
3. Trust past track records. Network Solutions took over a month to post in 2010, but posted reliably. Many people had concerns this year -- whether about the use of a discount code, or the confusion over 1000 vs. 2000 miles -- and the long wait didn't help matters, but in the end miles posted for most participants right on schedule yesterday.
4. If something looks broken, and veterans tell you it's broken, then it's broken. In prior years, US linked to an OfficeMax landing page containing a form for entering your US DM number. This year, there was no such page/form -- indeed, no way at all to type in your DM number. Various people made technically questionable claims about how OfficeMax could still credit the miles, all of which proved to be completely incorrect. OMX was a nuisance for everybody this year, but those who waited until 9/22 (when the DM entry form reappeared) ended up better off in the end.
5. Things I shouldn't have to mention. Register. Confirm with US that your registration took effect. And for God's sake, don't call a partner (or put comments in your hotel reservation form) and alert them to a loophole.

What other practical, general advice should we record for posterity?