My 7 year old bichon is a lovely natured dog. The one habit he has is licking wee. He meets other dogs and the first thing he does is lick their privates. He also licks where other dogs have had a wee. How can I stop him.
Regards

This is perfectly normal behaviour, especially from a male dog, and is nothing to worry about. It's how dogs greet each other and find what's going on. One of the first training classes I attended, decades ago now, told us that the dog sniffing and sometimes licking where other dogs had been was akin to reading their newspaper; they find out what's been going on in their world. :)

Some dogs seem to be more interested in this style of greeting than others so if it's not a new behaviour I wouldn't worry overmuch.  Teach a reliable leave or distract them.  I have a boy who will do this to dogs he's very familiar with.

For other readers however, it's worth knowing that it could be a sign of infection.  If you have a male dog that doesn't usually greet in this manner and has started to do it with a particular dog only then it might be worth getting that other dog checked (or mentioning it to the owner).  Check first if the other dog is neutered as that sometimes confuses adolescent dogs too.

My male starts "wee tasting" about a week before the girls come into season, this is normal for him and a very useful talent, he doesn't do it to the wee from my other male.

It is worth remembering that castrated males frequently smell to other dogs like an in season bitch, so this behaviour is probably just checking what he is dealing with. As with us who's urine is checked in hospital to check our health status so it is with dogs.

Yes my male tests the ground and then looks up with his teeth chattering as if to say "Aye aye, girl about to come into season" and within the week they always are...He's a treasure.

I discourage it with a 'leave' command away from home as he drags his ears in it....not nice!

with his teeth chattering as if to say "Aye aye, girl about to come into season"

Known in this house as 'clicking' because as well as the teeth the pricked ears click as if they have gone into spasm.

It happens here too. 

Always reminds me of a kiddies lower lip trembling, prior to bursting into tears!  :-)

Piglet does that to any bitch urine, regardless of seasons. Even where a spayed bitch has wee'd gives the same reaction.

I always think Rhuari looks like someone tasting a fine wine, he blows his cheeks out like you see wine tasters doing, only difference he doesn't spit it out.