Company Stock Purchase Plan

[PennStateFTW]

Hello all,

Longtime lurker with a great respect for many of the posters on this board here, and I've got a question about my company's employee stock purchase plan that I hope someone can help me with.

I'm beginning a new job on Monday that will let me purchase company stock at a 15% discount from the stock's market value on the last business day of each month. I have to hold onto the shares for one year before I am able to sell.

I am not sure about how great a longterm investment my new company is (it could be great, it could be poor; I am in the process of teaching myself how to value companies and am confident I will be able to do so reasonably well by this time next year, so I can make an informed decision about whether to hold or sell when I become eligible to do so), so my question is what percentage of my paycheck should I be allocating towards the stock purchase plan? 0% since I really shouldn't be investing in a company without knowing which direction it will likely head? 10% maybe? As much as possible since the stock would have to fall > 15% before I lose money?

Any help's appreciated.