The best way to accumulate Rewards quickly are with sign up bonuses for various credit cards with the main Banks and American Express.
The problem is the Reward programs are being devalued more often and with a greater impact to members of the programs.
My opinion outlined in a previous post is you need to model your Rewards portfolio in the same manner as an Investment portfolio.In that sense no matter where you travel and whatever Airline you use you will have a strategy to Travel at low cost just by using your Rewards.
The issue is the Big Guys either Marriott or IHG or Hyatt or Delta or United or British Airways or American keep raising the bar on the use of their currency then why bother at all in this Rewards Jamboree.
At this point the only logical answer is plan a trip and either use the Rewards you have now or plan a trip sign up for the bonus from the program or programs you think will work best and use them in a short time because they are losing value as I am writing this post.
All the major Hotel programs are watching each other lower the value of their programs where it stops no one knows.
So the mantra is Use it or lose it.