The first approach to knowing if someone on how to know if someone is having a crush on you is to trust your sense of judgment, then pay careful attention to details to know if he or she is really getting a crush on you. Below are some effective tips I culled from the internet and some life experiences from my close friends.
Portal One: From Social Media
They send you a friend request and start stalking you on Facebook, right after the first meeting. The social media is one place that helps show you if someone is 100% interested in you. Check who adds you on Facebook immediately after the first meeting. When someone follows everything you do on social media that is a good sign they are very much interested in you.
If they like and then unlike some of your old pictures on Facebook, it is an obvious sign they are stalking you. They will always make the mistake of clicking where they never intended to and try to undo it to cover the fact that they are looking up your details all the time. If they have no crush on you, there will be no need trying to cover their tracks.
They love texting you, even when there is nothing to talk about
When someone starts texting you often, it is a sign he or she has an obvious crush on you. If he/she form the habit of texting you through the day for no reason, he/she has developed deep feelings for you. Once the friend starts getting in touch despite how busy he/she is during the day, it means he/she can't get you off his/her mind.
Portal Two: Through Body Languages
Unusual eye contact
Once you notice your friend paying more attention to what you say without getting tired of looking at you more intently than usual, it means they have come to like you a lot.
They blush when they see you
Any friend that feels awkward around you has a crush on you. If he or she fidgets while talking with you, it is a crush. If the friend's face turns red when in your company or when you are talked about, it is likely he or she has a crush on you.
They try to look better than they normally do
Once someone suddenly starts changing his or her appearance, especially when they know you will be coming around, it shows they like you a lot. A good way to measure the change in their appearance since you came into the picture is to check their Facebook accounts. You will see an obvious difference in the photos they took earlier and the ones they take now that you are around.
Mirroring Your Body Language
Imitation has been shown as a very popular sign of attraction between men and women, and people copy people they have are attracted to without meaning to do so. Most times, they don't even realize it. If a friend starts using your favorite words and slangs more often and tries doing certain things the way you do them, it shows he or she has a crush on you.
They start hugging you more often
Having regular body contact shows a strong relation between the two of you. If you find any of your friends trying to sit or stand next to you whenever you are in a group, you should know what that means.
Portal Three: They show more care than necessary, they wish to know you more and get more involved in your life.
If they have a crush on you there are several ways they will try to convey their feelings to you. They will always find an excuse to be with you, talk to you, and care for you. They are often where you are. They care much about how you feel, and always try to make you feel better. They love taking you out for dinner, etc. etc.