tl;dr: Mine with
Replace-by-Fee v0.9.1 and you'll earn 1% more per block found, or 0.25BTC.
I'm running an experiment right now with replace-by-fee. Basically I'm doing continuously testing it, such that at any one time the extra fees from the test represents about 1% of the block reward. A site considering using the "scorched earth" defense to make accepting zeroconf transactions safer wanted me to get an idea of how willing miners would be to upgrade - I figured 1% would be an interesting starting point.
You'll need to compile and run the above tree. It's based on the v0.9.1 release with one small patch. Other replace-by-fee peers are automatically found on the network - you don't need to add replace-by-fee peers explicitly for it to work.
As for what this is all about, replace-by-fee simply means that rather than only accepting the first transaction you see to your mempool, you accept whatever one pays the most fees. It's a simple rule that results in the most profit per block, lets users re-issue transactions with higher fees if needed, and makes it clear to everyone that relying on unconfirmed transactions by themselves is insecure rather than giving people a false sense of security. Most importantly it ensures people use Bitcoin in a secure way, relying on crypto and incentives rather than relying on trust, which will help keep Bitcoin mining free of regulation and decentralized.
More info:
Why you should mine with replace-by-feeDouble-spending unconfirmed transactions is a lot easier than most people realize