Tension in the throat

 I consider myself an intermediate singer, because I do know some of the more advanced techniques, but I feel like there are some basic techniques I still struggle with as well. One of the biggest is a strong tension in the upper part of my throat when I try to sing high (usually in a mixed voice). It happens right at the "corner" where the chin starts to curve down to become your neck (like at the very top of the larynx maybe). I've had a few different vocal teachers, none of which could help me get rid of this tension. Any tips?

Without seeing and hearing you, I can't really give an accurate assessment. But I suspect that you may be feeling tension there if your larynx is sitting high (in which case I'd recommend "dopey" exercises to help the larynx stay relaxed and low, or at least neutral). Can you see or feel if that's the case?

I think it might be. If I put my hand above my larynx to kind of "hold it down" while I sing, it's seems to not be as tense.

Okay! It's very common for a high larynx to cause extrinsic muscle tension, as your "shout mechanism" takes over. Retrain your voice to sing those higher pitches with a lower larynx on something dopey and yawny (like MUHM or BUHB). You can also sing on a lip trill, thinking UH the whole time so your larynx stays neutral. 

I also encourage you to sing in head voice daily, and make sure you're "flipping" into head voice at the start of your warmup! This will encourage your vocal folds to stretch and thin out so they can do the same when you're in chest/mix. 

Head voice is another thing I struggle with. It's very weak and I've always felt like I needed to work on thinning out my cords. Sounds like being able to do that may also help with the larynx and tension. What's the best way to strengthen a head voice?

You mentioned hearing me sing might help, so here's a link to three songs I've recorded. One is actually a parody I wrote and it's in a pretty comfortable range. The other two are higher and I've been using them to help train my voice to sing higher. You can definitely hear where I struggle on them.

http://bit.ly/scottssongs

Here are a few great lessons on head voice and falsetto:

https://youtu.be/KaMJ9YvnUNw

https://www.youtube.com/watch?v=qxQOespT4Bs

https://youtu.be/-rfwlXnRbzY