I believe the most effective way is to live the transformed life the Bible talks about in Roman's 12 (see excerpt below). Merely telling people about Jesus isn't nearly as effective as living a life that is different, that people admire, that people want to have. That goes for both the real world, as well as the world of the DIS.
Look, I'm not saying that people shouldn't use the DIS as a means of expressing their faith. Many Christians do, and in ways that attract other to Christ. But some of you are doing so in a manner that is counter productive. If I can use you (Joyce) as an example (and I hope this doesn't come across as picking on you) but once you start getting into an argument about who is being more rude, you've lost any chance to witness to that person. Once you use your faith as a snappy comeback, there's no chance of the message reaching anyone.
Furthermore, you can't push your Faith on people. No skywriting, sticking tracks under windshields, etc. That pushes people away more than drawing them in. What does draw people is in that transformed life. Showing that Christianity isn't about where you spend Sunday mornings or having a get-out-of-heck-free card. It's about a life that isn't of this world, but is transformed into something better.
Romans 12:
2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God
9 Let love be without dissimulation. Abhor that which is evil; cleave to that which is good. 10 Be kindly affectioned one to another with brotherly love; in honour preferring one another; 11 Not slothful in business; fervent in spirit; serving the Lord; 12 Rejoicing in hope; patient in tribulation; continuing instant in prayer; 13 Distributing to the necessity of saints; given to hospitality. 14 Bless them which persecute you: bless, and curse not. 15 Rejoice with them that do rejoice, and weep with them that weep. 16 Be of the same mind one toward another. Mind not high things, but condescend to men of low estate. Be not wise in your own conceits. 17 Recompense to no man evil for evil. Provide things honest in the sight of all men. 18 If it be possible, as much as lieth in you, live peaceably with all men. 19 Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord. 20 Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head. 21 Be not overcome of evil, but overcome evil with good.
Can you just image what the world would be like if everyone that claimed to be a Christina lived their life this way?