There is a reason Shakespeare once said, "Neither a borrower, nor a lender be"—money has the ability to cause great turmoil in any relationship. We all have that one friend: they ask you for money, say they'll pay you right back and that's the last you'll hear of them. If you're lucky, they'll stick around to listen to you uncomfortably nudge them for your money and because you are a good friend, you ensure that your nudges don't make them too uncomfortable. But whether it's a hefty amount in the thousands or a menial one in the hundreds, it's clear what not to do when it comes to approaching friends who won't pay you back: be subtle.
But before you take any measures, consider this: why won't your friend pay you back? If you know of any financial troubles your friend is having, it's best to not pick around the topic of money, especially if the amount isn't too hefty. Maybe approach them once you know they're financially stable or set out a monthly payment plan that is suitable for both of you, stressing on the terms and conditions and how often the payments must be made. However, if this is a friend who has constantly defaulted payments, you should demand that the outstanding loans be repaid before even considering giving any more money to that friend.
I know, you hate asking for money because how uncomfortable it is, but it has been months and you really need your money to splurge on a new purchase. Admittedly, it goes without saying that you should give gentle reminders to your friends every few weeks. Your friend may have forgotten they borrowed money from you at all. However, if that fails, consider getting hostages, as in, collateral. If there is something you know your friend could not live without (like a PS4, a laptop or other valuables), ask to take it as collateral until their debts have been repaid in full. This can be a great strategy to incentivise your friend to pay you back faster.
Of course, if the amount itself isn't too big, perhaps it would be a good idea to write it off if it hasn't been repaid in a few years than to let it ruin a good relationship. At the end of the day, it's important not to let the lending of money interfere in your relationship, so if you can make do without the money, ensure you're not crossing any lines and don't be too aggressive in your endeavours.
It's great to help out a friend, but make sure you keep track of how much you're giving out in order to protect yourself from subsequent lending.