In addition to the other tips already suggested, genuine Louis Vuitton bags always have the pattern/material placed perfectly between seams.
So if half the word is chopped off on the right hand side, a genuine bag will have that exact same pattern mirrored on the left seam. If 2/3 of the circle symbol can be seen on the left hand side then 2/3 will be seen on the right hand side.
And the pattern will be level - ie.not sloping uphill nor downhill.
Here are some fake examples;
pattern slopes uphill - fake
pattern end on right not same as left - fake
same as above - fake
Remember that ebay-ers selling these items may not know themselves that their items are fake - best to protect yourself and ask to see clear close-ups of the sides and patterns. Don't get caught out.
As someone else has mentioned, a serial number and dust bag are as easily faked as the items themselves!
Good luck with your shopping and if you like/use this tip, vote and let me know