Generally, you'd have the best chance if you hadn't used the drive at all since you deleted the files. Every time something gets written on the drive, there's a chance that it'll overwrite the files you deleted.
Pretty much the best utility for this is Data Rescue. However, the proper way to do this would be to immediately shut the computer down and either boot from some other drive or put your machine in Target Disk Mode and connect it to another Mac. Then, you could download Data Rescue to that other drive and scan the disk from there. If you've scanned the disk with Data Rescue (using the detailed scan) and didn't see your file, you may have overwritten it already, and might be out of luck.