First decide what you plan to do with your library. Do you intend it to be used as an edit source or for playback only? If you simply plan to playback your material, you'll be better served by a digital format that compresses across several frames like MPEG-2 , which is the video format used on DVD's. In MPEG-2, there is one full frame of information every half second called theI frame which is encoded independently. The next frame encoded is a P or predictive frame, which anticipates changes in the video discarding redundant information. Between the I and P frames, B or bi-directional frames fill in, looking both backwards and forwards. MPEG-2 plays back I -BB-P BB P etc. Since most video has redundancy across frames, the method works well until there is a lot of change to your image as you'd find in fast moving color like fire. If you ultimately plan to edit your archives store your digital video in a format that uses intraframe compression. One such common format is DV.
Next determine the quality of your source material. A digital version of a VHS tape will still be no better than that original tape. All analog to digital conversion of audio and video is done by sampling, slicing the original signal into values that can be represented numerically. When it comes to video, the higher frequencies represent detail. The better the tape format, the higher frequencies it records. According to the Nyquist-Shannon sampling theorem, you only need to take samples at a rate of slightly over two per cycle of the highest frequency component of the source analog signal. In other words, you'll gain nothing by tripling or quadrupling the sampling which just increases the storage you'll need. Run tests of your conversion, before determining how you'll ultimately digitize your entire library. As an example, Betacam SP should be quite adequately served by 4:2:2 50 Mb/s AVI files while ¾" SP or VHS would need no more than 25 Mb/s I-frame MPEG-2.
Be sure to log your shots and sequences with date of shooting, on camera description, key sound bites with time accurate time code. There is nothing more frustrating than going through a library being unable to find what you need. The simplest way to handle this material is to store this as a text file, organized by time code at a location next to your video.
Either put your own edit system to work in the process, or find a local editor to help. If you are converting older tapes you might have to rent decks as video sources. Be sure to clean the heads of your source decks and load and unload a tape you won't miss several times before trusting your precious archive material on it. When it comes to some formats like ¾", you might have to run the video signal through a Time Base Corrector (TBC) before digitizing. Since this process creates a 1 frame delay in the video, ideally you want an audio delay line so the sound will stay in synch. Be sure to digitize tape by tape onto your edit system's RAID, hard drive array. Your system needs adequate bandwidth to make sure that you're capturing video properly. My edit system runs 6 15,000 RPM hard drives simultaneously. That's enough processing power to handle uncompressed standard definition video. My desktop has two separate drives, one of which runs at 7200, just enough to handle a mini-DV stream.
Once your file is digitized onto your RAID, play it back to check. Then transfer the file to a storage drive, where it can sit until you need to retrieve it. You can now pick up 1 terabyte USB 2 drives for less than $200. Ideally, you want to make a digital backup on a separate drive. Another option if you want to have immediate access to your archives would be to ultimately store your digitized library on either a Network Applied Storage, NAS; or a SAN, storage area network accessed by fiber channel. Once your library is digitized, you're preserved it for another generation.
Another option is to turn your tapes over to a one stop shop like Convergence Corporation at http://www.convergencecorporation.com
I've worked with Convergence over several years and can vouch for the quality of the conversions. The company also offers sophisticated handling of metadata for easy shot access.