He gave you The Look
In first-date language, The Look usually appears when a guy sees you and can't stop smiling and is basically behaving all cute and puppy-dog like. His eyes light up every few minutes, and he's genuinely interested in what you're saying.
Sometimes he even stares because he likes you so much. If you like him too, it'll give you a nervous-excited feeling in your stomach.
He tried to extend the date
If he kept trying to get you to stay longer, it's pretty obvious he couldn't enough of you and definitely liked you! You can look forward to the next one, honey!
He complimented you
If he likes you, he can't tell you enough how beautiful you are, how nice you look in that top, how beautiful your eyes are etc. One or two compliments might be an ice-breaker but a whole litany of them is a definite "Yes, I like you!"
He asked when he can see you again
You barely just ended your first date and he already asked when you two could go out again. That's a positive! Come on, he wouldn't want to see you again if he didn't like you, right?
He calls soon after
He's eager to see you again, or even just talk to you. He might not have call you the day of your date, but called a couple of days. You might have already fixed up a date to meet next, but until then, he wants to keep talking to you. Isn't that sweet?
Sometimes it's all very obvious and one or a combination of these signs will tell you if he's into you. It maybe harder at times, but watch out for these signs!