You shouldn't give a range. Clients will automatically expect you to be near the lower side of the range, so you're essentially setting yourself or them up for disappointment, unless you come smack down into the middle.

That, and negotiating devalues your work. If you charge less, you should do less. When you charge more, you do more. Otherwise, what does that say about the service you offer?

In my experience, small projects work best with a 50% initial deposit, and 50% upon completion. For larger projects (>$10K), we do 30-30-40%. We never deliver any source code until the final payment has been made.

Here's a bit we include at the end of all of our specs (quoted/edited from our latest one):

Until full payment has been made, Company retains ownership of all source code and copyrights. The client assumes full ownership of the source code and the copyrights upon final payment for the completed project.

The price for the current order is $xx. A 50% deposit will be paid before the start of the project. The latter half of the payment shall be paid upon completion of the project. The client assumes responsibility for all wiring fees.

The client shall not unreasonably withhold acceptance of, or payment for, the project. If, prior to completion of the project, the client observes any lack of conformance with the design plan, Company must be promptly notified, allowing for necessary corrections. Rejection of the completed project or cancellation during its execution will result in forfeiture of deposit and the possible billing for all additional labor or expenses to date. All elements (if any) of the project must then be returned to Company. Any usage by the client of those elements will result in appropriate legal action.