1) He'll hide his emotions for a long time.
There exists 4 kinds of guys -- one having a very masculine mind, one who's more towards the feminine side, one somewhere in the middle (average), and one who're really players with full intentions.
A) Feminine kind is the one who shows to the world that they're soft and emotional. So they're popular with the girls, cause they can 'connect' to him. They see that unlike normal guys, he's emotional and sentimental. These guys will usually not cheat cause they respect women and their feelings and emotions NOT because he really loves the girl. It's hard to make these kind of guys fall in love.
These kind of guys usually do not have a strong sex drive (cause they got low testosterone), so they can easily make a girl just 'friends' without seeing them as sex object. In contrast, guys with high or average testosterone (average/high sex drive) will always see the girl's body and there's sexual tension involved if she's attractive. See
http://www.scientificamerican.com/article.cfm?id=men-and-women-cant-be-just-friends
However if he treats her as a sister, then he won't be objectifying her.
B) Average guys show to the world that they're masculine, hard to some extent and are less on emotions (more 'manly'). However they do have a soft emotional side but they take these things personally which they'll revile to their very very close friends and girlfriend. This's the reason why they avoid girls, cause these guys are mostly talking about real world things instead of themselves, their sentiments and emotions. And girls talk exactly about these things and these guys not comfortable reviling these things to anyone. So both the genders loose interest in the small talk, so these guys have less female friends than A).
http://en.wikipedia.org/wiki/Small_talk#Gender_differences
Since these guys tell about their personal stuff and emotions to their GFs, they become very close to her and unlikely to cheat, but they can be stolen if other girls get him to talk about these personal stuff. He's going to treat her as a friend, but cause of higher testosterone levels as compared to guy A, he will be objectifying her.
Average guys are the highest in quantity (that's why they're average). Guys and girls had to be faithful otherwise humanity would not have succeeded. The average guys and girls have a good degree of faithfulness so they can take care of the child which's critical to success of humanity. So in case you think normal guys are not faithful, you're wrong. That cant happen. Otherwise we humans would not have made it.
C) The masculine guy -- This's the more extreme version of the average guy. If you have this kind of boyfriend, getting his personal emotions and stuff out of his mouth will be hard, but once you get it out of his mouth, he'll be like your personal dog.
If you got the skill, you can make this guy all LATTU over you. But he'll be overprotective and overly concerned about you.
But these guys have high testosterone, they objectify ANY stranger girl and that stranger girl may steal him from you by getting to know his personal stuff; however this's very hard to do and unlikely to happen, cause these guys are very shy when it comes to these things. Then these kind of guys have very less female friends. If they do cheat, they'll do it only for sex, and that's probably cause you're not giving him enough, and he's getting frustrated cause of that.
On the outside these guys show themselves to be emotional morons and 'though' guys. They're very keen to prove their masculinity and feel very insecure in case their masculinity is threated. However on the inside they're equally sensitive.
To ensure these guys wont cheat, get him to talk about his emotions and his insecurities on a regular basis and you'll get your most faithful partner.
Also you need to give him more physical, cause he needs them to satisfy himself (it's a REQUIREMENT). You can see these guys hanging around in forum.bodybuilding.com.
So overall, these guys are hard to maintain, but they'll love you till death.
Yeah and 1 more things -- these guys are VERY honest to their beloved GF from deep within their hearts. They wont fake their emotions and it's very easy to tell if they're lying or not, cause they're not good at pretending things. See --
http://www.medicalnewstoday.com/articles/251411.php
So you can easily see when he'll just starting to cheat.
D) The players -- these guys are like B, but they're truly bad. They don't care about others, and willing to do any damage to others for their own benefit. Since he's like B) he got his emotional side and he knows it. He hides his emotional side from the girls so he doesn't become attached to her and often lies about it. So what you girls got to do after a while (like a month in India) is that stop telling about yourself and ask about HIM and his emotional side. Most players will elude when you'll do this.
2) His phone remains busy -- That's cause he's talking to other girls most of the time. He hopes he'll get in most of the girl's pants. His phone remains busy for long amounts of time continuously -- that means he's talking to someone long. Some other girl. If it was some work related talk, and he's in general busy, it'll be busy from time to time instead of continuously.
3) He got a lot of female friends and makes a lot of new ones. -- That's cause he's searching for new targets. He needs girls to cheat with and get sex right? If a guy has no female friends, how will he cheat? Every attractive girl he sees is an opportunity, and he's going to at least try. As a result, he got many female friends, almost all of them attractive. Then if he loves you, he should distance himself form other girls --
http://www.livescience.com/24755-oxytocin-men-fidelity.html
4) He wont tell you about his female friends even when you ask and wont introduce them to you -- That's cause if you both talk, you'll realize the game he's playing. If he's not a player and yet friendly with the girls, he'll gladly introduce all of them, cause there's nothing to hide.
5) He's good in impressing girl with his talk. One thing players get that other guys don't is experience with girls. They know exactly what girls like, what charms them, they'll figure out what type of girl she is and talk accordingly. And that's the reason why he has many female friends.
6) He looks at girls hard. Guys always checkout girls. But when they're not single, they just check out. It's like -- "Hay that girl got great boobs" "WOW great figure!" "she got nice skin" etc... And that's it. It ends there. If a guy is noticing a girl or staring at her for 10 or 15 seconds from time to time, then it means he likes her and he's planning to move on her. He's looking forward towards the 'opportunity'.
7) He often targets beautiful girls. Beautiful girls get players and cheaters most of the time and are more cautious. Normal guys looking forwards towards a relationship don't even look at them.
8) He does dirty things only. -- Suppose you gave the guy access to some of your private parts. Instead of doing stuff like -- holding you for a long time, kissing, putting hands on your waist, kissing your face (forehead, cheeks, nose etc...), kissing your hands and arms etc... he's go directly to the cherry and will always try to enjoy the cherry without any warm up or doing anything as stated before. He only does stuff like squeeze or grope your breasts, always putting hands in your very hottest body part like the butts, breasts, or genitals. He'll only do a passionate kind of French kiss but no or less casual kissing.
9) He does not share his stuff. He's listening most of the time, and avoids talking about himself. This's to prevent him from getting involved (as explained above).
10) He does not complaint. And he likes everything about you. This can't be a coincidence. In his mind "Just bear this girl till I get in her pants, and then I'll be GONE". So, in case you're bothering him very much, he wont complaint much. He'll lie and show you he's doing whatever you want; serious guys on the other hand won't lie like this.
11) He doesn't give a damn what you're doing. Hanging out a lot with another guy? Going on date-like situations with him? Telling him about this 'guy' while still saying you like him? Starting a new bad habit after sharing with him? If he does not mind most of the above, then it means he really doesn't care. That's cause all he wants is to get in your pants.