Clean them well, shoot them and enjoy them. I will say though that if you start to think about "customizing" them, you can quickly end up with a lot more money sank into a mediocre rifle than you would have paid for a factory rifle. I'm not a purist, I have done it myself, just saying: you're not going to save any money going that route. It's something you need to want to do just from a "tinkering" standpoint.
That said, they can be fun, but the increased prices these days are turning me off of them. I've got a lot of good milsurps saved up at this point, and they were all pretty cheap (Turkish Mauser - $40, Yugo Mauser - $70, Yugo SKS - $90, Schmidt Rubin K-31 - $90, Mosin Nagant M38 - $65, SMLE No4Mk1 - $70). Those are my unmodified/untouched examples - got a few more sporters. At those prices, they were good cheap fun at the range. With modern prices seemingly getting to $175-200 for most of them though, they're just not as fun IMHO. I like milsurps for the price, but when they reach price parity with older used commercial rifles, I tend to start looking at the commercial ones instead. They are designed with recreational shooting in mind anyways (scope mounting options, lighter weight, handier barrel lengths, etc). Rather than milsurps I find myself looking moreso at rifles like the Savage 99 and such.
Again, just my opinion there. On the plus side, if prices keep going up, I may get a good opportunity to translate some of my milsurp rifles into commercial guns via trade.