I and i guess a lot of other players struggle with callingranges. Callingspots and Pushingspots are the basics and also the most important elements to win a SnG or MTT.
While pushingspots are easy to learn from any position and any stacksize (beside the few adjustments against some regs and also fishes where you can make -EV pushes very profitable) callingranges differ from that.
There are some approaches in poker and i guess it always depends on your style of playing which you prefer. Which leads to the first argument Jonathan Little made:


"From time to time you will find +EV situations you should pass up. Late in tournaments you have many chances to go all-in if you are shortstacked, but you should pass on some of these, because if you lose on one +EV marginal play, you will lose the opportunity to make more +EV decisions later. Suppose you think that pushing in a situation will show an expected profit of +0.25BB. This isn't much! So you should probably wait for a spot where you can profit 1BB or more."


Here he is referring to pushingspots, which are profitable based on nash, but very marginal overall.
On most tables, you usually have an edge, if you work on your game on regular bases. You just can't realize this edge, if you make such marginal moves. This is a general statement and it is useful for pushing and callingspots. Let's see what else he wrote about callingspots!


"If someone pushes ahead of you, you need to figure out his range and your hands equity against this range. The most common situation is when everyone folds to the button, who goes all-in for 10BBs. Assume the small blind folds and the action is on you, with 50BBs in your stack. There are 2.5BBs deadmoney from small blind and antes and you have to call one big blind less because you already have 1BB in the pot. So there are 13.5BBs in the pot and you have to call 9BBs more. To figure out how often you need to win simply compute (9/(9+13.5)) = 0.4
You must win 40 percent of the time against your opponent's range to break even.
Notice that the pushers position only matters in helping define his pushing range. Your position is important because if there are a lot of players left to act, you should be much tighter than if you are in the big blind with no players left to act. If you are not closing the action, you need a much stronger hand to call.

From here simply plug in the numbers to determine the hands with which you should call. For example, if your opoonent is pushing 50 percent of hands, you should call with something like 22+, A2+, K2+, Q8+, Q6s+, J8+, J7s+, T9 and T8s+. I would call with all these hands if my tournament life isn't at risk. Notice that you actually need to be slightly better than 40 percent to call, because you want to do better than break even. Consider tightening up a bit more if losing the hand will put you out of the tournament. If I were short, i would probably call with something like 44+, A5+, K8+, QT+, Q9s+ and JT+. This gives up a tiny bit of equity because you are folding a lot of the worst hands that you could call with, but you will gain the equity back, plus more, when you have the opportunity to push in the future!"


In this part is one of the most important statements for myself! Give up a tiny bit of equity in really close spots and just fold hands which are +EV when your tournament life is at risk! But what hands should you call? How much equity or expected value do we need for a call? In the previous statement Little claimed, that he like to win 1BB with each move. I think this number is a bit too high in sng formats in most spots. In multiway spots, when my tournamentlife is at risk, it's really the least amount of expected value i want to get. In 1 vs 1 spots i'm happy to get it in with an expected value of about +0.75BB (sometimes less) or higher.

Let's look at an example hand by Jonathan Little.

Example:
"Suppose the action folds to the player in the small blind who has 8BBs and you know he will push any two cards. For thos example i will use chipgs, although leaving numbers in terms of big blinds works fine as well. Assume you are playing 200/400-50. There are 500 in ante chips, plus your 400 in the big blind, plus your opponent's 3200. So there are 4100 chips in the pot. You have to call 2800 more, so you need 40 percent equity to call. You want to be better than break-even. So you need around 43 percent equity to profit. So you simply use 100 percent for your opponents range and determine that you should call with 22+, A2+, K2+, Q2+, J2+, T3+, 95+, 86+, 76+ and slightly worse suited hands. When players play poorly on your table you can call a bit tighter. I would actually call with something like 22+, A2+, K2+, Q6+, J7+, T8+ and suited connectors."

Here you can see what the exact callingranges look like in HRC, when you illustrate this situation:



He pretty much always aims for at least +1BB value.

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In the book: Sit n Go Strategy by Collin Moshman you find a bit different approach.
He advices everyone to pick up every +EV callingspot. He don't really make general statements about it, but in the given examples in his book he just calls whenever it's +EV.
The main problem in his examples is, that his tournament life never is at risk in close spots. And when his tournament life is at risk, he always have hands with more than +1BB of expected value.
The only real statement he made is following:

"If you are getting better than 2 to 1 on a preflop all-in and your call closes the action calling is nearly always correct"

Overall i think he has actually quite similar preferences to Little when he have to decide if he should take a +EV situation, if his tournament life is at risk.

Here is a short summary about the usual questions people ask:

When do we call with hands which have worse than +0.75 to +1BB outcome?
-When your tournament life isn't at risk
-When you don't have an edge over other players on the table

How do we set up ranges on unknown opponents
I think it's bad to give them the range that you will push as a bit more experienced player, even if you tight it up. You should always consider, that they push really tight and make calls based on that nitrange!

How do we learn calling ranges?
Reviewing a lot helps a lot! But usually just make following:
Make standard ranges, which you give either regs or unknowns. Look up how certain hands perform against this standard ranges.
Ingame you should just use following numbers, to estimate your winchance of your hand.
If you get 1:1 odds you need 50% equity.
If you get 1,5:1 odds you need 40% equity.
If you get 2:1 odds you need 33% equity.
If you get 3:1 odds you need 25% equity and so on.
So if you are getting 1,8:1 ingame you are somewhere between 33% and 40% which means you should usually call, when you know that you have about 36% against his range when your tournamentlife isn't at risk. Mark close spots, look them up after your session and you will get a beast in callingspots!

Kill everyone
The mental game of poker
The theory of poker
The math of holdem
The raisers edge
Sit n Go strategy
And the books which are mentioned above