Good question. A combination of a few things:

+ Attach yourself to a story cluster if a relevant one is already there by linking to a source post

+ `tip @techmeme <url>` on twitter

+ Message the editors on twitter

+ Make sure your feed validates, can be autodiscovered etc.

+ Techmeme can discover stories based on retweet counts, so make sure the same canonical URL is being retweeted and favorited from the post, from twitter, disqus etc.

+ Post interesting things frequently enough that you become a source that is crawled by Techmeme

Good advice. I wondered why/how I got included on Techmeme before. I would assume it is based on "Techmeme can discover stories based on retweet counts,".

TM takes hints from a lot of sources - including HN. It has 30k+ sources that it directly crawls itself as well, and uses a lot of different hints to work out what is popular. The biggest hint to a big story is inbound links from other blogs that are also sources, and from there things like popularity on social media