There is nothing as scary as a lockout. You shall be left short of ideas on how to move on from that point. This is why you may see someone trying to smash their way into their car, or breaking down their door. This means that you should have a plan of action before things get to that level. There are normally plenty of options made available to you when you think of who to call. You need to know which one of those to call as they come up. It is expected that the first thing you shall be looking for is one who can come to the scene quickly. But apart from the fast response, there are other things you need to be wary of.
Most of the locks we have on our cars and buildings have gotten sophisticated. This higher level of security shall present a bigger challenge than what locksmiths used to handle in the past. You, therefore, need a locksmith who shall come equipped with the knowledge of how these state of the art locks operate. They may have been easy to lock you out, but unlocking them will not be as easy. You cannot afford to call a service provider how shall come and start guessing what to do. That will only escalate the situation from bad to much worse.
You then need to call a service that is available around the clock. You never know at what hour there may be a lockout. It can happen at any time. Too bad if that time is at night, and there are no neighbors around, or you are stuck in some far off place on your journey. You therefore need to first find a locksmith that offers round the clock services and emergency response. Then save their contact details for those emergency situations. You may have to pay more for such emergency response services at odd hours, but at least you shall be safe.
You also need to see hat payment options they are comfortable with. No one goes into a lockout situation with all manner of payment options, least of all cash. You cannot also be expected to be composed enough to go to the bank to get the cash when you just faced a lockout. They need to be open to card payment, or electronic ones. You cannot also be expected to have cash handy for making such payments. If they cannot accept card payment; you need to look for other services.