This thread suggests helping out by clearing up casual observations with missing data:
Ways to help out on iNat - wiki
As @cthawley says it’s probably best to target new users or recent observations. I just discovered that you can change the new user (Account Creation = In the last week) filter from the default by editing the url after you’ve selected it. e.g. if you want accounts in the last 2 weeks change &user_after=1w to: &user_after=2w