You'll need ratchet straps (or motorcycle-type straps) to secure it on a trailer (or in anything else), or adequate rope and good rope skills to secure the smoker to anchor-points or bed-rails on the trailer. Be sure to secure the lids so they will not open in transit. Small and light-weight trailers tend to ride very rough, so anything loose (not hard-mounted) inside the smoker such as grates should be removed and put into a container. Also, consider your analog thermometer(s)...if you use them for chamber temp monitoring, it would be best to remove them and package for transport, as shock from a rough ride may damage them, or at the very least cause inaccuracy, so cal-check/verification should be done after transport if left in place. Lastly, be sure all smoker leg, handle and shelf fasteners are properly tightened before and after transport.
Good luck and have a great smoke!
Eric