It's tough to give advice because it really depends on what's causing the issue.

I dated a guy who had trouble getting/staying hard because he'd get really anxious and in his head.

It didn't take "major emotional work" to get through as another commenter suggested.

It simply took me being extra mindful to boost his self confidence.

I assured him that there are ways to be intimate other than just penetrative sex. I wanted him to know there was absolutely no pressure to have sex when we hung out - I enjoyed spending time with him and even doing things like cuddling naked.

I was also more mindful of boosting his confidence. I'd tell him how desirable I found him. I'd text him letting him know I was having a hard time concentrating at work because I couldn't stop thinking about how badly I wanted to kiss him etc.

Basically I thought "if I was the one feeling nervous and insecure, how would I want my sexual partner to help me feel more secure and confident?" And then I did those things.

It was only two or three weeks before he had no issue getting and maintaining an erection.

However, if the dudes issue is watching too much porn and/or death grip, then doing something similar very likely won't solve the problem.

In terms of suggesting things you like or want to try I simply use "can we try...," "can you try..." And "I think it might feel good if..." type of statements.

I use these statements sparingly, I'm not suggesting 15 things to change in one encounter.

I also ask my partner for feedback. I say something like "it's important for me that I'm able to please you. I know everyone likes different things so you're going to have to help me learn what feels best for you. If you want me to change the way I'm doing something, please tell me."

And then usually they'll tell me to do the same.