1) Set up a pool, explicitly stating that purpose of this pool is 51% attacking LTC. Before the attack begins, mine like a normal pool.
2) (optional) Set up a pool which will also be used for 51% attack, but doesn't state that (looks like a normal pool). Don't do that, if according to your opinion, it is unfair play, immoral, etc. But such a pool is an important element of the attack.
3) Cooperate with a botnet, share future profit with the botnet owner (or maybe you are yourself a botnet owner). When the attack begins, ddos normal pools, they will go down and miners will automatically switch to the second attacking pool (the only pool which looks normal and not ddosed). Also use the botnet for mining.
4) Improve this plan, I'm sure it can be improved.
Why might you want to participate?
If you are among several key people, leading the attack, you will know date and time of the attack for shure and will be able to make money shorting LTC.
Many bitcoiners will participate in the first attacking pool, just because they want to do that, and somebody finally provides an opportunity.
Even if you are litecoin miner/investor, or just a simple guy never refusing making easy money, you might be interested in helping this attack. Being smart, you will be able to estimate approximate date of the attack. To make profit you don't even need to shortsell LTC. Just sell you coins and buy them later, during massive selloff which will follow the attack. You can either earn USD/BTC keeping the same amount of LTC, or increase your share in LTC.
Shame is the way that LTC handles mining makes this possible. I'll x-post this pertinent snippet from this thread:
http://www.reddit.com/r/Bitcoin/comments/1bcr1s/why_is_difficulty_set_to_10_minutes_per_block_why/The different hashing is a silly idea of making things "equal" for miners. Whomever made litecoin wanted to stop GPU miners from having control, so they put in a memory hard hash instead of the SHA256 hash. But then of course it transpired that people can do this on GPUs, so they rebranded it to be ASIC resistent.
In reality the more dedicated miners like ASICs result in a safer block chain because in the Litecoin world, someone could build a really expensive but functional FPGA or ASIC at some point and completely take over the market. The artificial limits that Litecoin imposes on mining growth due to the mistaken notion of 'fairness' ultimately cripple miners' ability to secure that blockchain as effectively as Bitcoin's.
edit: so yeah, this is the real chink in LTC's armor. Once LTC grows to a sufficient value where it would be profitable to execute such an attack the whole LTC market will be at risk.