It can be hard when you have feelings for a straight guy, especially if he doesn't know that you're not straight.
It's a tough situation to be in, and there are several different scenarios to consider before really asking the question "how can I tell my straight guy friend I have feelings for him without offending or scaring him away?" (Also read Best Ways How to Talk to Your Crush If You are a Gay and He’s Straight.)
Let's look at the first possible scenario: he knows that you're gay and doesn't mind it. How can you tell him you have feelings for him without offending or scaring him away?
You don't want to be too straightforward about it. Start with a simple casual conversation that will eventually lead to you to confess your crush on him. That way, he won't be taken aback. (Also read How to Tell a Friend You’re Gay and You Love Them.)
It would be a lot simpler if he was your best friend. He would definitely understand and wouldn't think much of it nor would he make a big deal out of it. If he can see the point of view you're speaking from, then he won't see it as a huge problem.
You might leave him speechless, or maybe you won't. Either way, you should listen to whatever he has to say. Listen to his thoughts, even if they may sting a little.
Now let's look at the second possible scenario: he doesn't know that you're gay, and you don't know if he doesn't mind it or if he does. This is far more tricky, because it's kind of like trying to wake up a sleeping dragon.
If you're careful enough, then the dragon won't wake up and you'll make it out alive, but if you're careless, it'll wake up and you might just end up dead. So how can you tell him you have feelings for him without offending or scaring him away?
This is similar to the first scenario, however this time it's more like trying to tame a wild lion. You have to choose your words carefully that if he's susceptive enough, he'll understand where you're going. (Also read How to Tell Someone You’re Gay Without Saying It.
Don't hide it. It may be normal for someone who's gone through a lot of rejection to hide their feelings, but if you're confessing to someone, it's better to let everything out. (Also read How to Tell If Your Gay Friend Has A Crush On You.)
Sometimes the situation can be unpredictable, so just prepare yourself for the worst. Rejection is one thing, but he might come to a point where he doesn't want anything to do with you anymore. But you know what? That's okay, because you're worth more than him, and you no longer have to spend your time and energy on someone who won't accept you for who you are.
No matter how he reacts, what matters is that you stay true to yourself. Love yourself over everything else.