Well, I've seen several discussions of this topic on different boards, and one of the things that someone will always say is that you're a good diver if you have a good attitude and you're trying. But you know what, I disagree with that. You're not a good diver if your basic diving skills aren't good, no matter how nice or earnest you are or how hard you are trying. I guess what I'm trying to say is that most new divers aren't good divers . . . YET. But they can be good companions underwater, and I enjoy diving with them.
To me, there are a LOT of characteristics that go into making up a good diver. Good in-water skills are part of it -- The ability to place yourself where you want to be, in the position you want to be in, and stay there if you want to. The ability to reduce the impact on your surroundings to the degree that's necessary or desirable. The ability to solve problems underwater to the degree that's appropriate to the dive in question. Facility with one's equipment. Facility with emergency procedures (air sharing, mask replacement). Those are all physical diving skills that a good diver should have, IMO.
Then you add situational awareness, which includes but is not limited to buddy skills. Knowing where you are, where your buddy is, how the conditions are changing and what implications that has for the dive plan, what resources the team has (gas, equipment, knowledge) and always keeping in mind the limiting parameters of the dive (eg. need to return to the anchor line or find the shore exit).
But then you have to add the experience and judgment to assess a dive accurately and make good decisions about its advisability (and some of that is related to varying amounts of risk tolerance). To do good dive planning, including collecting the necessary information about site and conditions, and planning gas supplies and time parameters for the dive. Selecting appropriate buddies and shore support, if needed. Obviously, you need to do very little of this to paddle around the Honey Bear, and a lot of it if you're going to try Deception Pass.
And then I'll add a couple of criteria that are personal to MY definition of a good diver: I think a good diver has a lot of respect for the power of the water and the alien nature of where we go, and never loses that. And to me, a really good diver has some humility, because all of us could be better at one or more things. And the final characteristic that makes me admire a diver is generosity. The people who command my greatest respect are the ones who spend some time giving back to the diving world -- For example, the folks who were involved in the recent Big Buddy dive.
By my own definitions, I have a ways to go to reach the "good diver" level. But you don't have to meet all those criteria perfectly to be a good underwater companion and a good buddy and fun to dive with. I've had extremely enjoyable dives with brand new divers whose buoyancy was iffy and whose ability to avoid silt just wasn't there yet, but they were so joyful about being underwater and so excited about what they saw that it was a great time anyway.
The one non-negotiable demand I have is that buddies stay together. If you're unwilling or unable to do that, you don't go in my list of good divers and you don't go in my address book
"Sometimes, when your world is going sideways, the second best thing to everything working out right, is knowing you are loved..." ljjames
. So the question is, What does it take to be a good diver, or what attributes do you look for in a regular dive buddy? Is it training, buddy awareness, comfort level, number of dives, equipment configuration, strokability 
reliability, common goals? Tell us what it is that you think makes a good diver good, and how you choose your buddies.
As long as we all know the signal, I can live with either one 
