Smell them.
If it is fake it will most likely say Gucci on the belt buckle but if its real it will not and the stitching mite look a bit wavey or sloppey
You know it is real when you look inside and it says Gucci(r) and the bar codes are inside.
the matterial should be very fine for real gucci and on the back of the watch it should say gucci stanless steel and where it is made.
Usually when gucci glasses are real they will have a number on the inside and be made in Italy. Fake ones don't have a number and are made in China.
One hint is that they should be made in Italy. If you contact the actual manufacture they will often help you verify as well.