What is your target ratio of Concentration spells to Non-Concentration spells on your character list.  I know this can vary based on many factors; but this discussion should focus on how many spells you feel comfortable having access to while concentrating on one.  What is the strategy you use for a spell selecting process?  Or do you not feel there is a risk in loading up on Concentration spells as long as you have that one go spell for encounters? 

Thanks for your input and the discussion. 

I tend not to worry too much when selecting a spell whether it's concentration or not. I find that, unless you're really going out of your way for it (or if your build has a very limited number of spell selections) you'll generally end up with a decent spread of concentration and non-concentration spells.

I think what you actually have to be a bit more picky with is how many spells you take that have a casting time of a Reaction. It can be overwhelming if you have 3 or 4 different reactions you could be taking each round... although I suppose for some players, that versatility is more valuable.

I tend to go for at least 1 non-concentration spell of each spell level.

I want one or two concentration spells in each of my highest levels.

No more than one concentration spell in the middle levels.

My lowest levels I keep no combat concentration spells.

For example, 5th level WIzard I might take only the following concentration spells:

3: Haste and Hypnotic Pattern

2: Web

The rest would be non-concentration.

This gives me enough to concentrate on two or three battles and still have spells to spam enemies with.

I aim for:

A couple of concentration

about the same amount of "I can cast whilst concentrating on that" spells

always aim for 2 or more Bonus Action spells

at least 1 Reaction spell

I also look at what the concentration spells do. I don't worry about spell synergy with, say, Polymorph, because I'll usually be smashing things as a large beast by then.

I think it can really depend on the specific spell. Some are more in combat, others out, where you don’t have to worry much about say, locate object overlapping with spirit guardians. But once you have spirit guardians, you’re not going to use other concentration stuff in combat, really. Or I should say I won’t. 

Then, for a warlock, I prefer concentration spells, to get more use from the limited number of spots. 

I basically just ensure that I have at least one or two go-to non-concentration spells that I can cast while concentrating, generally ones that cover cases that my cantrips don't.