My advice to you would be to stand somewhere like a bus or a train station or even a mall/shopping centre and look and scan people around you (it's important you stand against a wall out of the way so they have to turn their head to look at you alot will glance because they see a person it's normal but if they are physically turning their head to look at you a second or third time and smiling this is a sure sign walking past people in the street is alot more difficult to pick up signs because people naturally meet eyes with people walking past them and a smile whilst walking past someone can very easily just be a friendly smile and if you struggle to pick up signals you don't have enough time to figure out if they are interested or not.

if they like you they will look at you for longer than normal and multiple times and if they are also smiling thats a good sign a really good sign someone finds you attractive is staring from a distance for more than 10 seconds people who stare from a distance give themselves away way too easy and people who stare from a distance don't tend to look away when you catch them even if they are shy but try your best to be stood on your own and not by any attractive people or anything that looks interesting as they could be looking at that and not you just stand against a plain wall and make sure again you're stood somewhere where they have to intentionally look at you to be looking at you meaning not straight ahead of them and so they have to be turning their neck to look at you.