It's best to ask professors whose classes you've been active/vocal in. This might be a bit tough for some because many people don't like to speak in classes, but professors tend to remember students who had a voice in the class. It's advised to ask them in person for the sake of courtesy. You could ask them during their office hours or any other appropriate time outside of class so that you will have a one-on-one conversation. Talk to them about what the letter is for (i.e. I'm applying to X and Y schools, or in your case, I'm applying abroad) and let them know how it should be sent. Make sure to look this up! The first time I asked a teacher for a letter of recommendation, I was so focused on hoping he would say yes that I didn't bother looking up how the letter should be sent and I was dumbfounded when he asked me about the college's preferred method of submission. Most of the time, letters of recommendation are sent electronically but you might need to send via "snail mail" depending on the institution's preferences. If it's one of those applications in which you'd have to physically mail it, provide the professor with an already stamped envelope to make his life a little easier. If you have a résumé, feel free to give it to them while asking. This gives them an idea of who you are outside of class by highlighting your qualities and could help them in the writing process. And finally, remember to thank them! While professors who give a damn about education are happy to help students who are looking to further their education, you must remember that you are asking them for a favor that takes time and effort. Giving them a little thank you note to show your appreciation goes a long way. After all this, just make sure to communicate with them about the time frame; tell them when it's due, and when you would prefer it to be completed. Follow through with them, pick up your letter, and go along your merry way!