Can I wash saddle with soapy water? How can I take care of my saddle?
My saddle is the GT MTB Saddle, which is made from synthetic materials.
It depends on the type of saddle.
Leather saddles should generally be kept away from water and conditioned periodically. There are many pages on maintaining a leather saddle such as this one and this question and this FAQ from Brooks -- see the documentation that came with your saddle (or find the details from the manufacturer.
Plastic/Vinyl/other synthetics are generally quite hardy and should be fine with a gentle soap and water (but check with the manufacturer of the saddle -- yours may be different). They generally don't require any upkeep. While probably not ideal, I normally use a Clorox or Lysol wipe on my saddle when I wake up and find that a squirrel has defecated on my saddle -- I'm not entirely sure what makes squirrels like bicycle saddles.