Where do you work?
I work for Boots doing Customer Care, approaching customers is my job too
Some people don't like being approached, tbh women are more approachable than men, IMO. If someone looks like they can't find something, that's the best time to approach them. 1 in 10 of these people will just be looking for someone, but they don't seem to mind you asking them.
Some people don't want to be approached, and occasionally
you'll be approached by customers asking for help. Just be friendly with a smile on your face and don't get pissy if they don't want your help. I had a (seemingly) rude young American man in my first few weeks on the job but I think that's just the way Americans are, seems rude to us but normal for them. It was annoying but you have to remember your job is to wander around the shop floor looking for people who need help.
If you can think of something in your store that is particularly hard to find, and work out the demographic for those, it might make things a bit easier for you. For example, in my Boots store, all the mens stuff is upstairs but not a lot of people realise we have an upstairs, men unfamilar with the store often can't find it.
I honestly just walk up to someone who looks like they need any help and ask if they're looking for something or if there's anything I can help with. I'd say about 50% of customers are looking for something, the other 50% aren't.