Without knowing what type, style, size of boat you are looking at I can only make some general suggestions. First and foremost be sure the trailer is roadworthy and not a rusted out piece of junk. How high up does the boat sit on the trailer? The taller the boat sits the farther in the water the trailer must go and this presents problems retrieving. Side guide are a big plus to help center the boat on the trailer, or does the trailer have centering rollers? Full roller trailer can make centering easier than many bunk style trailers, but many things can be done to make centering easier on bunk style trailers. Short tongue trailers can be more difficult to backup and require backing further into the water so be sure you have plenty of tongue forward of the bow of the boat. Be sure the boat is totally supported by the trailer supports all the way to the stern. All of these general ideas can and will make launching and retrieving your boat much easier. Usually things can be added or adjusted to make loading and retrieving a boat much easier.
