Unless you never take your camera out of the bag, it’s unlikely that your lens will be dusty or smudged but hopefully there are some signs of usage to them. When I started purchasing my first lenses, I was more exciting by the mere fact of owning them but I neglected looking into how to properly taking care of them. Luckily, I’ve taken amazing care of them so they’re in mint condition. Kerry Garrison’s video on properly taking care of lenses was the first video I saw.
His simple advice is:
Don’t do any rubbing, don’t do any blowing to them. A simple Lenspen and a rocket blower should be your tools of choice for cleaning your lenses properly.
Normally I purchase everything through Amazon but I found a Lenspen on Ebay for $5 with free shipping.