Ask
I am in complete agreement with Shot on this. You should try never trick anyone into anything.
The easiest way to get use of locations is to ask. The trick, if there is one, is to be professional, both in the way that you approach them and in the way that you behave on the shoot, if they give you permission.
This means telling them exactly when you need the location, for how long and what you will be doing. Once that is agreed, make sure that you stick to that and that you leave the place in the exactly the same state it was when you walked in. This means having a realistic understanding of how long it will take to set up, how long to get the shoot rolling and how long to bag up at the end. Nothing makes a location situation go bad faster, than only having half the work done in the time you've agreed for the location. This will be bad for your reputation and for the film. It is when you rush things that mistakes are made.
The other thing to remember, is that to undertake a shoot on location you really must have insurance in place for the shoot. That way, if you do have a redhead explode (it does happen) and set fire to their carpet, the insurance covers it. if you don't have insurance, then you personally will be liable.
The truth is, that providing you are professional about your approach, it is rarely difficult to get locations.