How widespread is OP_RETURN forwarding and mining (as of February 2014)? As of now (February 2014), how easy is it to have a transaction which makes use of OP_RETURN data confirmed into a block? 

Do standard nodes forward such transactions yet? Have major mining pools committed to support? 

Are there specific steps that can improve the chances of such a transaction being mined, like connecting to certain nodes with advertised support, or adding extra transaction fees?
It will take until bitcoind version 0.9 for wide spread support for relaying OP_RETURN.

Adding fees will not help. Currently, transactions with OP_RETURN are by default not relayed by the main net (last sentence):
https://en.bitcoin.it/wiki/Script#Provably_Unspendable.2FPrunable_Outputs

P2Pool seems to accept them, so that could be a solution for you: submit them to a P2Pool node.