Always, I mean ALWAYS, start off every image file name with the yearmonthdate_ followed by the number. For my own personal work I use the date followed by the original file name so I can easily find the RAW file again, however for your clients you will want to renumber them all starting with 0001. Clients tend to get fussy over seeing image breaks. They think you forgot to give them those files when in actuality you deleted them due to poor image quality, eyes closed, etc. I also include a one word description at the end of the file name so they can easily sort through them on their computer.
Here is how the file name should look:
TIP 1: Use underscores for information breaks and all lowercase. This is basic computer etiquette in proper file naming.
TIP 2: Image numbering should be consistent. If you only have 99 images, then start your numbering with 01. If you have 10,000 images start with 00001. Since I usually have over 1000, I use a four digit label: 0001.
TIP 3: keep the description short. If it is too long (20090429_0450_familygroupformal.jpg) your image may not read on another computer.
TIP 4: Why start with the year then the month then the day? If you start with the month: 04292009 you will end up with potentially out of order files since 0429 will come up again next year. If you start with the year, your files will never be out of order because 2010 will always come after 2009.