Safety is something many guides overlook. Nothing is more critical than making sure your guests are safe. Always carry an emergency medical kit on your person. Band-Aids are particularly important because feet tend to blister from all the walking associated with sight seeing. At your earliest convenience take a CPR training course.
Assess the general physical condition of your guests when you pick them up. Follow this up with inquiries about where they have come from and how their trip has been so far. If they look tired or sick simply ask them if they are ok to do the tour today or if they would like to postpone it. Postponing your tour can be a hassle but it is much better than dealing with a guest with diarrhea or worse yet having to revive one that collapses. People on vacation are sometimes in such a hurry to have a good time that they forget to eat and drink enough water. This combined with the extra energy needed to travel can be a dangerous combination. If the person appears to be in bad physical shape, if they are grey, bright red or obviously sick put your foot down and insist that they seek medical attention. You will be surprised how stubborn people can be. Preventing a serious incident while they are in your care is the primary concern.
Another safety aspect consideration is to avoid dangerous places and activities. If you can’t avoid treacherous places you might want to get your guests to sign a waiver clearing you of any and all responsibility. Remember that your group will be walking slowly, looking around and taking pictures. They and you will obviously be tourists. In many cities locals have no problems but thieves target tourists. Call your local police station and ask them where they publish their crime statistics. Then look those stats up and plan your guided tours around problem areas.
Take public or professional transportation such as buses and cabs rather than using your own car. Driving is a very dangerous activity and as a guide you don’t need the extra responsibility of driving your guests around. In addition to the liability, it is difficult to concentrate on your tour if you are driving. Lastly, driving your guests around adds a level of intimacy that might not work to your advantage. If you have a nice car maybe your guests won’t feel like they need to tip you. If you have an old car maybe they won’t feel comfortable or safe in it.