This is a question that was asked by Luke Labeau in an article written by Robert N Rossier in the March / April 2017 edition of Dive Training. 
The answer is multifaceted, but mostly involves the single most important tool of divers, COMMUNICATION! That being said, here are a few ideas:

• BYOB (Bring your own buddy!) Before planning a solo dive trip, see if anyone at your local dive center, or club can introduce you to someone who might like to join you in the outing. If you are on a charter, talk to the other solo divers and see if their dive style matches your own, including how much territory they want to cover,(do they like to swim fast and cover a lot of ground, or do they like to take their time and observe things more closely?) How they do safety stops, and anything else you can think of that might be a sign of compatibility. 
• If you are inexperienced, see if you can be partnered with a divemaster or other experienced diver who doesn't mind diving with a newbie. Just because a diver has more experience does not mean they will not make a good buddy for a newbie. Sometimes a more experienced diver might be a perfect match for a newbie if they enjoy the same type of diving and do not mind serving as a mentor. 
• What really helps a buddy pair work together is how they communicate before they even begin the dive! Talk about the dive. How long? How deep? What about hand signals, navigation, and emergency procedures? And don't forget to check each other's equipment!
• Finally, if you are on a boat, and have concerns about finding a compatible buddy, talk to the captain or dive leader. They might be able to help find you a compatible buddy. If it goes well, great! If not, ask them to pair you with someone else that matches your diving style better. 

As you can see, all of these tips come down to communication! Talk to the dive center before you go, talk to the other divers, and finally talk to the captain or dive leader. As long as you are straightforward about what you want, you can make it a great experience for both you and your buddy!

Certified divers should have a pretty good understanding of how to dive safely. Still many find themselves in unsafe diving situations such as diving beyond their means, or diving despite fear or discomfort. 
​According to Jason Martens, Ph.D. in his article "The Social Psychology of Safe Diving", in Alert Diver magazine published by DAN, there are many reasons this can occur. Some of the ones listed are things like "diffusion of responsibility", which is when we see something wrong but say nothing because we assume it is someone else responsibility to do so. "Deindividualization" which is when a person feels like they are lost in the crowd and may act more impulsively. "Normative social influence" which leads people to do things they know they shouldn't to get along and be liked. And, "Informative social influence" which is when we do as others do because we think they know best. (Happens to novice divers quite often!)
So, how do we counter these influences? Well, Jason has a few suggestions:

• Take Control. Don't assume someone else will speak up if something is wrong. Review your training! If it looks or sounds like a problem, speak up! Someone else is probably thinking the same thing, but too shy to say so.
• Slow Down. We tend to act impulsively around other people, so slow down and think! A few seconds can save a life!
• Play Devils Advocate. To help avoid going along with the crowd, try to think of all the things that could go wrong. You never know when it may help you notice a potential problem. 
• Rely On Your Training. Part of being safe, is recognizing unsafe diving. If you are unsure, ask! Ask a diver who seems to be demonstrating a commitment to safe diving by their words and actions. Or consult your manual!
• Be A Good Role Model. If you are a safe diver, then do not be afraid to go out of your way to make sure others recognize it. Help novices that seem to be struggling. 
• Role Play. Practice what you would say if someone asks you to make an unsafe dive. It is easier to respond if you have already rehearsed the right thing to say!

Most divers know the risks of cutting corners, rushing dives and not being fully prepared. However, if we can recognize the things that lead to these conditions, we can help keep everyone safe.