With the mortgage credit crunch, and so many would be borrowers now unable to finance property, landlords now have a much larger pool of qualified tenants to rent to. Unfortunately for prospective tenants, this means that landlords have the luxury of being much more picky about who they allow to rent their properties.
Therefore, landlords have begun looking more closely at tenant credit scores, and past rental history. Being a landlord myself, I have much experience with bad tenants, although I do have a screening process to vet potential tenants. The difference between a good tenant and a bad tenant is the same as the difference between making money and losing money in the real estate game.
As a tenant, if you can pay several months rent in advance, and/or setup automatic monthly drafts of your bank account to satisfy your rent, you can stand out from the crowd of prospective tenants looking to rent the same piece of property.