I think you will find this article about taking wedding photos extremely helpful.
http://www.digicamhelp.com/learn/places-events/wedding.phpThe author makes the point about letting the professional wedding photographer do his or her own thing but then gives a ton of useful tips for persons like you and me who also will be taking wedding photos.
If you take photos inside using an external flash, you may want to consider getting a bounce card to get a softer look. I don't know what model you have, but some Alpha models have higher noise than some DSLRs at ISO 800 and 1600, so try not to go over ISO 400 if you can.
If you have time to set-up, you may wish to use a tripod for staged, inside shots.
Oh, and don't forget to take extra batteries and memory cards. Some of these accessories are touched upon briefly in this two part articles about DSLR accessories:
http://www.digicamhelp.com/accessories/dslr-accessories/top10-2.phpAs to different complexions, I'd expose for lighter skin tones and yo can always bring out detail in darker skin tones when you edit. Hopefully someone will come along that has an alternative take on this.
Test your camera and settings before the wedding begins.
Good luck, and let us know how you do if you time permits.