LOCATION, LOCATION, LOCATION

I don't know if any of you have ever tried to secure a location for a movie shoot, but it can be a headache. A lot of people I've spoken to seem to think that all they need is permission from the owner. Simple, right? Well let's look at a couple of standard situations and see what's actually needed.

The House, Office, or Other Interior.
First off, you have to find out who the owner is, not the renter or the leaser, or the manager. The owner. Then you have to get a location release form signed, which generally requires the filmmakers to have insurance to cover any possible (and, sadly probable) damages to the building. Then, is the owner of the building going to let you use their furnishings? Probably not, so now you have to go out and get your own. If you're filming in a house, you probably don't want to be moving stuff in and out too often, so the owners of the house will need to not be there while you are using their house, but they have to be somewhere. I've known filmmakers who sent the homeowners on vacation. It's expensive, but at least they didn't have the homeowners barging in and freaking out about the hole in the wall. Either way, you have to keep on schedule because when your time is up, your time is up and the owner will want their space back. Also, owners always have the right to change their mind and kick you out, no matter how far along you are. It is, after all, their building.
After it's all said and done, there will be nicks and bumps on the walls from jostling gear around that you'll need to repair.

The Sidewalk
Getting permission for this is fairly straight forward. Most cities have film offices and all you have to do is contact them, usually through their website. Some cities have no-film areas or other restrictions, they'll let you know. The fee for filming will vary, depending on the size and scope of the shoot, and unless you're a very small operation, you'll need to have your production insured. The difficult part comes when you go and actually try to shoot. Everyone and their dog wants to be in the movies, and so quite often there will be people who will do everything in their power to cause problems until the you agree to let them be in the movie. If your sidewalk scene requires traffic to be stopped and/or controlled, or if there's any sort of violence/weapons in the scene, then you'll need to pay for at least one police officer to be on set (minimum of 4 hours of pay, regardless of how short the shoot is), and their presence can sometimes help with rowdy passersby.  If you splurge, and the city allows it, you can take over the whole area, locking it down so only your people can be around. Generally, locking down a city block is too expensive for all but the Hollywood Blockbuster.

The Park or Other Public Space
Very similar to the sidewalk, though you'll be less likely to need police (unless you have violence/weapons in the scene). The exceptions come into play when you want to get into public spaces like Historical Sites, Protected Land (National Parks are an example), and Public Transportation. All of these are, understandably, a bit harder to get permission for filming. Your chances of getting permission will vary a lot depending on what you're wanting to do in the film. Most Protected Land is only available for filming when the film is directly related to the land, like a documentary or nature program. Public Transport is out in almost every case, if only because it interferes with the public transport, not to mention the safety risks. Historical Sites are particularly tricky because any damage to them, no matter how small, is unacceptable. They're Historic Sites for a reason, and repairing them is ridiculously expensive.

The Studio
If you have the resources to shoot in a studio, building your own sets, enjoying total control over the surroundings, then you really better not fall behind on schedule or go over budget because your budget is probably already quite large, and any overage is going to be proportionately large.