Well I can speak from experience on having lots around and not getting a shot from my first year. Manged to fix a lot of mistakes and get a nice one in my second year but here's what I did wrong:
1. Watched too many videos-okay maybe they helped more but I did have at least three times where I was waiting for the perfect open shot and should have shot a gobbler. When they are filming those hunts it's more important to them to get good footage rather than a kill. To correct this I went in the bush and practiced shooting plastic Pepsi bottles in bush situations. I got better at estimating range and capabilites of my gun. I realized I had a few times where experienced hunters would have been yelling "shoot that thing!"
2. Busted by hens - couple times I had gobblers coming in. I was so focused on them I didn't pay full attention to everything around me. When the toms were behind trees I would adjust my position to get ready for a better shot. Next thing I know I have a couple hens I didn't know were there see my movement and send out the alarm putt and the jig was up. I learned to be a statue until I am literally ready to shoot.
3. Trying to set up to close-heard the gobble moved up closer to it. as I'm deciding where to set up I see the white head running away. Sometimes as you see on the videos they come running FAST. It had always happened where they hung up so i didn't think moving would be an issue and I get a runner! Learned it's better to sit tight on the hung up ones and try different things to bring them in. Moving in on them is too risky.
4. Rain is good! - learned that when it rains they like the open areas. rain in the bush hides sounds and so they get in the open where they can use thier keen eyesight to spot predators as opposed to hear them. This narrows down where I go to set up on roosted birds knowing better which way they are likely to go. Shot my gobbler in a thunderstorm using this tip I learned. Now I don't curse at a rainy day I see it as an opportunity.
5. Don't leave, be patient- if you have the ability to sit for long periods of time then do it. My very first moring I had a gobbler answering my calls. I had him engaged but never saw him. After an hour or so of silence I decided to move to another location. When I got there I realized I had left a call on the ground where I had been. before leaving for the day i went back to get my call and you guessed it. There was a tom and couple of jakes wandering around right where I had been. I learned that they probably were intercepted by hens in the morning but later after they were done they headed back to the spot where they had heard me calling earlier.
6.Call them uphill not downhill-I hunt in ridges and I had a few times where i was set up halfway down a ridge and they would call at me from the top but wouldn't come down. I know always find a way to get set up on the ridge top. Last year i called a jake from the bottom of the gully right up the ridge to within 10 yds (unfortuneatlye the big tom that was with him on the limb didn't follow).
7.Learn mouth calls-I was busted a couple times messing around with my friction or box call. Hunting alone I would have probably shot one in that first year if i had learned to use the mouth call for those final 50 yds or so. A lot of the manufactures have "beginner" mouth calls and it was like riding a bike. Once I figured out the basics on a beginner all the other ones that I previously couldn't get a sound out of worked like a charm.
I am sure I mad other mistakes and still do

but those are the few that clearly caused my missed opportunites.
Good luck!