Something that's advisable makes a lot of sense — enough so that you'd recommend it to a friend. For example, it might be advisable for you to go visit a college before deciding to go there as a student.
Use the adjective advisable when you talk about actions that are completely wise and fitting. It's advisable to change the batteries in your smoke detector and wait for the walk sign to cross the street. It's also advisable to save some money every month and to consult your entire family before bringing home a puppy. Advisable comes from the verb advise, or suggest, with its Old French root, aviser, "deliberate, reflect, or consider."