Use headphones to monitor sound, especially on the wireless mic.

Put new batteries in all wireless mic transmitters/receivers.

Be prepared for harsh backlighting or frontlighting when filming in evening light. Be prepared to manually adjust exposure to compensate.

Put lots of foam around mics. Put lavaliere wireless on groom or minister/rabbi/whatever. If really windy, tuck partly inside the shirt. Will be muffled, but may be better than having wind noise. Check before ceremony, if possible.

Put a camera near the altar and let it crank, unattended. Audio can be very useful, and video is useful for cover shots.

If sound system is used, plug one camera into that, if possible.

Go here for the most popular wedding videogaphers site:

http://www.videouniversity.com/forums/gforum.cgi?forum=16;

Last summer, one of the mags, DV or more likely Videomaker had a extensive two-part article on just this.

Look closely at what is in the background of your shots - amazing what can sneak in un-noticed out of doors!

jrazz, about a week or so before the wedding, take your camea out to the wedding site, and shoot some footage at different angles. You might also want to get some baseline/background audio while there. You know, birds, crickets, the streetcar that runs by every 10 minutes, etc. Back at the 'office', check for sun spots - these will quickly mess up wedding shots-nothing like a big ole' sunspot dancing between the bride and groom at the altar. You might want to think of a "rain coat' for your camea and soundgear - just in the weather goes sour. Depending on your location, you might want to figure out a way to keep your tapes comfortable - June could get awfully warm. Also, going to the scene will give you an advance notice on the terain, and how you going to truck all your gear to the shoot site. You might have to invest in a camera light for the reception afterwards -however, by June it will be staying light longer. Remind your clients, bad lighting could equal bad video. Hope some of this helps.

Here's my 2c on sound:
Use cardiod mikes on each wireless, mic each speaker (bride, groom, officiate) separately. Use wind screens without fail.

The reason:
If you use the lazy studio/stage approach of depending on one or two omnis to pick up all the voices, what you will end up with is airplanes, wind, crowd chatter, crickets and little else.

Trust me on this. Been there.