Wedding venues are really, really good at charging you the absolute maximum possible as they know this is the one of the areas where people go nuts in terms of spending. Some tips from my experience:
1- The 22% service charge is the least likely thing to change; depending on your location, this is fairly standard
2- Alcohol: if it is a hotel/restaurant, etc, it is unlikely that you can do much to change this. However, if it is a venue that is just rented out for events, some will let you buy the alcohol yourself and then just charge you for serving it. This could cut down cost significantly especially if you choose a few types of beer, wine, and alcohol as opposed to a complete bar with every choice imaginable. Costco is great for this. If you really want to bring the cost down, do beer and wine only and then one boozy drink like rum punch or a "signature cocktail." If the venue won't let you buy your own booze, ask to limit it to just beer, wine, and your signature drink and avoid the cost of a full open bar.
3- Extra hours: I've never heard of getting this reduced or waived.
4- Site fee: the best way to reduce this is to do the event on a Friday (weekdays are usually cheaper). The other option is (if date hasn't been set yet) to do the wedding during your venue's "low season" if there is one. Most venues will negotiate a lower price for using an off-peak and non holiday weekend.
Hope this helps!