If there is a Gmail account tied to the phone (there will be one if the market app has ever been accessed) you will be prompted after 20 incorrect attempts at the lock pattern to enter the Gmail credentials to bypass the lock pattern. If you don't know the username or password for the correct Gmail account you can try Gmail account recovery here. If you're unable to enter the Gmail username/password or never had one set up, your only option is to follow the instructions posted by Infected100 to perform a master reset. I hope this helps!
As a last resort you can wipe your phone clean and reset it to how it came when u purchased it.. without being locked out.
To wipe your phone clean:
1) put it off by taking the battery out
2) Once off, HOLD the volume down button, and then push the power button until the screen turns on (while holding the volume down button)
3) Let go of all the buttons once the screen does turn on
4) using the volume keys to cycle through the options and the power button to select.. choose "Clear storage"
This will remove everything that was stored on the internal storage (texts, call logs, apps, notes, etc). But if you paid for any apps, they of course will still be avalible after you set up again. It will not remove the things on your SD card (music, videos, pictures) so you wont have to worry about that at least.
Hopefully you can find another way to do it before deleting everything off your phone :/ good luck
Actually my daughter has placed a lock pattern on her HTC EVO shift and has forgoten the pattern. Is there anyway to reset it or how do i clear the pattern to open her phone?????