@maxdancona,
I would skip the part about the "economic outlook". Not only does this sound threatening, it isn't a good way to appeal to your landlords better side, it also isn't true. The fact is that in almost any place in the country the rents are going up meaning that the landlord could probably raise the rent and get another tenant without too much problem if she wants to.
You are asking for them to not raise the rent. You probably do not have very much leverage. My strategy would be to start nice. The tone of the letter should be that you like living there and hope that the lease can be renewed at the same rent. Say you you like living there and would like to renew the lease at the current rent.
Then if they say no, find out how much they want to raise the rent. Then decide what your bottom line is and negotiate from there (or find a new place). You may have some leverage (not much) because changing tenants has some cost to them. But wait to find out what they want in terms of rent, and then negotiate from there.
The other option is to not even send a letter and to let them make the first move. This is a common negotiation strategy... the first person to make an offer in any negotiation (in this case they would have to tell you how much the new rent is) generally ends up bending more. Wait to find out what they want to do, and then try to negotiate down from there explaining that you are a good tenant that they really want to keep.