Ok so I've already done a tip on what to say when you are texting 'him' I'll add the link to that when I'm done! But the first step is actually getting his number!! By the way I've tried all these with different guys and they all worked for me!
1-) The prank call
Ok so this way you need to get his number from one of his friends or your friends and prank call/text him! Then he will be like 'who is this' or 'leave me alone' and then you say oh ahhah its _____(Whatever your name is!) Bam instantly he has your number if he's interested he'll text you on it!
2-) The excuse
Easy, simple and highly effective. 'Oh hey can I have your number I need to ask you about the homework project' 'Oh hey can I have your number I need to call you about math' 'Oh hey can I have your number I need to text you something later' etc.....you get the idea!
3-) The flirt
If you guys have a flirty relationship going on why not just throw in a blatant 'You should text me sometime ;)' Just go right ahead and give him your number! And don't forget the flirty wink!
4-) The friend
Ask his friends for his number! Or anyone that has it !
5-) The casual
Just ask him plain out! Make sure to keep it casual though if you aren't sure he likes you, you don't want to seem desperate!
FUN FACT: Well its not really a fact but one of the cutest times a guy has asked for my number was I was going through my phone contacts and boasting I had 106 peoples phone numbers then he said to me: 'Wanna make it 107 ;)' I'm pretty sure girls can say this too but I just wanted to share it with you its so adorable :)
Lots of love,
Oooh by the way here is what to say once you have his number :)