I received the above question on Formspring, a site that allows people to ask questions of others. You may have heard about it on the news; in some places teenagers are using it to heckle other teenagers. I'm not using it for that, as you can see below.
The book of Ecclesiastes says "Remember also your Creator in the days of your youth, before the evil days come and the years draw near of which you will say, 'I have no pleasure in them' " (http://esv.to/Eccl 12/). The writer of Ecclesiastes tried everything he could think of to make himself happy - entertainment, money, superior knowledge, sex, everything. What he discovered was that anything you do in your life apart from God is meaningless. The point of the book of Ecclesiastes is to start out early, when you are a young person, following after God's will for you... and then when you get older, you won't have to look back and say, "Well, THAT was a waste of time!"
Now, as to "how" to follow God so that you don't one day look back and say that... I'm afraid that's not a question that can really be answered for you by somebody else. You probably know some of the key things you can do: learn everything you can about God's Word, spend time praying and worshiping God, that sort of thing. Another key is found in 2 Timothy 2:22 - "So flee youthful passions and pursue righteousness, faith, love, and peace, along with those who call on the Lord from a pure heart." (http://esv.to/2 Tim 2:22/ ) By "youthful passions" Paul wasn't just talking about sexual passion (although that certainly qualifies) but he meant that you should remain cool-headed and not make big decisions based on the emotion of the moment. Check every decision against the Word of God and the voice of the Holy Spirit within you (meaning, pray about it and then listen to what God says back) and you won't spend your life messing up.
It also means that there are times when you literally should "flee" something that you know better than to get mixed up in. Recently a woman was telling my wife and me about how proud she is of her teen-aged daughters, who have a habit of calling or texting their mom when they are with friends and it looks like things might go in the wrong direction. "Mom, call me and tell me I have to come home right now!" is a text message she's received several times from her girls. They are fleeing from a situation they know they don't want to be in. A famous example of this "get out of there!" strategy is found in Genesis 39:1-23. (http://esv.to/Gen 39:1-23/ )
I would advise you to read that passage in Genesis, and also take a look at Ecclesiastes. Ecclesiastes can seem quite depressing (because the author was kind of down when he wrote it), but you need to look at it as an example of what will happen if you do not choose to follow God. I can't tell you step by step exactly what to do to serve Jesus - I don't know your situation (where you live, what needs might be around you that God might call on you to fill, what your gifts and talents might be, etc.) but I do know that young people face temptation (old people do too!) and need to resist it. And I do know that God had something in mind for you when He placed you on Earth, and He has no intention of keeping it a secret from you. Hook up to him - plug in like plugging lamp into a wall socket - by getting your mind filled with what the Bible says and by spending time in His presence in prayer and worship, and when the time comes for you to make a decision about what to do with yourself, make your decision based on God's counsel and not your own "youthful passions" and you will do just fine.
Now, as to "how" to follow God so that you don't one day look back and say that... I'm afraid that's not a question that can really be answered for you by somebody else. You probably know some of the key things you can do: learn everything you can about God's Word, spend time praying and worshiping God, that sort of thing. Another key is found in 2 Timothy 2:22 - "So flee youthful passions and pursue righteousness, faith, love, and peace, along with those who call on the Lord from a pure heart." (http://esv.to/2 Tim 2:22/ ) By "youthful passions" Paul wasn't just talking about sexual passion (although that certainly qualifies) but he meant that you should remain cool-headed and not make big decisions based on the emotion of the moment. Check every decision against the Word of God and the voice of the Holy Spirit within you (meaning, pray about it and then listen to what God says back) and you won't spend your life messing up.
It also means that there are times when you literally should "flee" something that you know better than to get mixed up in. Recently a woman was telling my wife and me about how proud she is of her teen-aged daughters, who have a habit of calling or texting their mom when they are with friends and it looks like things might go in the wrong direction. "Mom, call me and tell me I have to come home right now!" is a text message she's received several times from her girls. They are fleeing from a situation they know they don't want to be in. A famous example of this "get out of there!" strategy is found in Genesis 39:1-23. (http://esv.to/Gen 39:1-23/ )
I would advise you to read that passage in Genesis, and also take a look at Ecclesiastes. Ecclesiastes can seem quite depressing (because the author was kind of down when he wrote it), but you need to look at it as an example of what will happen if you do not choose to follow God. I can't tell you step by step exactly what to do to serve Jesus - I don't know your situation (where you live, what needs might be around you that God might call on you to fill, what your gifts and talents might be, etc.) but I do know that young people face temptation (old people do too!) and need to resist it. And I do know that God had something in mind for you when He placed you on Earth, and He has no intention of keeping it a secret from you. Hook up to him - plug in like plugging lamp into a wall socket - by getting your mind filled with what the Bible says and by spending time in His presence in prayer and worship, and when the time comes for you to make a decision about what to do with yourself, make your decision based on God's counsel and not your own "youthful passions" and you will do just fine.