Well, it seems that you are quite interested in this particular field. So, as far as I know, according to some cases, people would blink more frequently when they are trying to tell a lie, and their hearts will beat at a faster rate. Anyway, if the personal blink more than they often do, then probably they are lying, but it all depends, since some liars are professional and experienced.
There are lots of methods for you to see whether a person is lying or not.
First of all, watch to see if he makes eye contact. A person who is lying typically avoids eye contact.
Secondly, you ought to observe where he or she is looking. Wandering and fidgeting eye movements tend to indicate deception. Also, looking down and to the left is an indication of fabrication, while looking down and the right indicates true remembrance.
The others thing you cannot ignore is looking for dilated pupils. They are more common in liars than truth-tellers because lying causes stress and dilated pupils are a sign of stress.
Last but not least, notice if the expression of his eyes matches his statements. A person who is making a happy statement like, "I love you!" shouldn't have a furrowed brow and squinting eyes.
It is really a hot and big topic to explain. It is related to the so-called micro-expression study. I once saw a serial soap drama named lie to me, which is focusing on how micro-expressions help the star to crack tough case he met. The micro-expression will only last for about a fifth of a second, hard to catch. It is a natural and instinctive reaction to what people heard and saw. If the expression on people's face, it might be fake. If someone is lying, you can see the expression on his/her face means different to what he/she is saying. When someone is preparing to lie, he/she usually look directly at other's eyes to convince the people who are listening to him/her. Yet, as I said, it is a big topic. If you are really interested in it, I suggest you to buy some books on this topic, which could help you learn more.