I really don't need to say more than the subject, but please, your mobile phone is an important part of your life, may even be your latest fashion accessory! 

If your phone starts doing wacky things it has probably been wet.  If you come into the shop where I work and demand a new one or that I repair the old one I will tell you that if it is wet it will be returned unrepaired and you will be charged for the piece of paper telling you what I just told you for free.  How to tell if your phone has had any liquid in it at all?  (Even 'pocket sweat'.) 

First, is it dripping?  That's fairly obvious.  Take the battery off, put it in the hot water cupboard and hope for the best.  And don't bother bringing it in for repair. 

Are the little connectors at the base all corroded?  That's a sure sign.  Did you take off the back housing and battery and check if there is a nasty pink (or red) sticker in it?  If you have a sticker under the battery and it is white then it hasn't got water on the sticker, at least. 

If it's red or pink, consider that you have just saved yourself a minimum service fee!  (And don't bring it in to me!)  Why am I so het up about it?  Because I don't like being abused when I have to charge you for sending a wet phone away.  Oh, yes, and you are given a warranty card when you buy your new phone, and it clearly states that physical and liquid damage void your warranty. 

And warranty only applies to the original owner.  (Which means you are covered if it was bought as a gift for you!)