Greasing the axles & wheel bearings
From Ninja250Wiki
Greasing the axle is simple...Spray the axle with cleaner, wipe clean and then apply a layer of fresh grease. Any standard grease is fine...Bel Ray waterproof grease works for a lot of MC needs (and trailer, and car, and bicycle). If there's too much, it'll get scraped off. This isn't of Huge importance for streetbikes that live indoors....
As for the wheel bearings, you just pry off the dust cover, and then force as much clean grease into the bearings as possible. Some people like to clean them first (flush with parts cleaner), but just having grease in there is FAR more important than having Clean grease in there (so long as the dust covers stay intact). Anyway, you force the grease in with your fingers. It's messy, but simple.