That's part of the beauty of chess: there are no rules, no concrete formulas, merely principles. Cherish your opponents for giving you the opportunity to stretch your knowledge, and use it--all of it--regarding piece coordination, weak and strong squares, seizing the initiative, control of the center, king safety, and so on, everything you know and also the things you haven't yet worked on. And a further hint: don't trade unless it gives you an advantage or improves your position.
Playing against unconverntional moves
If their unconvential move isn't attacking you, isn't threatening anything, then don't worry much about it.
Continue to develop your pieces. When possible, develop one of your pieces with an attack on one of theirs. That way, they have to move that piece again, and you gain a tempo - and can develop another piece.
Develop your knights/bishops, castle, bring you rooks to files that are open, or which are likley to open up.
And watch for tactics where you can win a piece.
Just because a move is non standard doesn't mean you can take advantage of it right away. They may be pushing pawns because they don't know what to do. You can let them push pawns, while you develop pieces. Then you'll have your pieces developed, and their development will be far behind.
After you've got your pieces out in the game, castled to safety, etc, then you can look for ways to attack. Since they aren't playing the way a stronger player would play, you should probably be able to control the center.
Don't trade just because you can. Trade when you can gain something. If you can use a trade to break up their pawn structure, leaving them with doubled pawns, isolated pawns, that sort of thing, then your stronger after the trade. But if the trade allows them to develop a piece when they recapture, that leaves them stronger.
Play with the Tactics Trainer here a lot, and you'll start seeing oportunities to use tactics in your games. Those unconventional moves they are using are unconventional for a reason. As your tactics improve, you'll start seeing more chances to take advantage of them.
And study basic endgames. If you know how to win in basic endgames, and they don't, then simply trading off pieces will leave you in an endgame which you can win. IMO, beginners are better off learning basic endgames than studying openings.
I'm a beginer player and I've been trying to improve my game by playing against my friends. But I've run into a problem. When I practice with a computer or players on this website, they all play standard openings and strategical moves. But since my friends don't know openings, they play whatever comes to mind, or make their own strategical decisions which are really unorthodox. And I find myself unable to get a proper advantage because these moves confuse me. I knwo that unconventional moves should be capitalised and taken advantage of, but I have been finding it difficult. So I try to trade off and get into the endgame. But I want to know how I can get an advantage over a player who has no idea about openings and plays almost randomly or with an unconventional strategy?