Is the yard owned or rented? It is not unknown for rented yards to be asked to leave with very little notice or, having not paid their rent to be ousted off PDQ! This could leave you and your horse in a precarious situation.
What do you want to feed your horse? If you´re happy to go along with everyone else that´s not a problem, but some yards won't allow your own feed choice. Heck, some yards here don´t even stock any kind of forage whatsoever! Make them confirm that they would feed what you ask and whether you´d purchase it or they would, confirm the price for this either way.
Be prepared to pay a deposit. A good yard will require this, and most likely the signing of a simple contract. After all a horse is a luxury item to keep and the yard needs protection, just as much as the owner, if they find themselves with unpaid livery bills.
Do you want to ride? Well, silly question of course. But if you want to school, is their an adequate arena to do so, and what are the rules regarding it´s use? If you want to hit the trail, do they have any, many, some or just the road you came down? Most liveries in Spain do have great trail riding straight from their door, but just as many have nothing but roads or dry river beds. Take a walk, or better still, rent a horse from them and go for a ride before you decide.
Does the yard close any day each week? This is important to know. If the answer is yes, ask who and when feeds the horses, should your horse be under veterinary care can you still go the day it is closed to dress wounds or attend with the vet and, is there anyone on sight who would be keeping their eye on the horses ´just in case´ and have the knowledge to deal with any given situation, or know who to contact if not?
Insurance. Ask what they have covered and what you are expected to cover.
What kind of yard is it? Is it a competition yard, a training yard or do they just provide livery? If you have a youngster you need help bringing on, the friendliest of yards is no use to you if they don´t have people with the knowledge to assist with that.
Can you bring your own professionals in? Yes, incredibly some yards wont let you use your own trainer, hoof carer or bodywork specialist. Be sure to clarify that.
Hygiene and health. Do they have a worming and vaccine schedule? If providing turnout, how often, and are the paddocks poop-picked and/or rotated? How would your horse be introduced and integrated to a new herd?
Observe: Are the facilities in good, cared for condition? Is there a hard stand for grooming, hoof work? Is there a wash stall? Are fences and gates in good order? Are there alternatives if a horse can´t go out? i,e; a horse walker, or turnout in the sand school. Is there access to water and electricity on site? (and is it included in the cost?) What does the accessibility and general security look like? Does someone live on site or do they have CCTV?
Be Honest If you contact the yard owners of any yards that seem suitable, be honest about your horse’s behaviour and your experience. Some yards will not tolerate horses with certain vices- such as weaving or crib biting, and other yards do not allow children or dogs - so there is no point moving to a yard if any issues like these are likely to be a problem. And if your experience is limited and you go to a like-limited yard, the blind will be leading the blind and in the long run your equestrian experience will not be a fulfilling one.