The Bible says in Hebrews 4:12 "That the word of God is living and powerful, and sharper than any double edged sword, piercing even to the division of soul and spirit, and of joints and marrow, and is a discerner of the thoughts and intents of the heart."
We see from the text that the word of God by the power of the Holy Spirit is living, powerful and sharp. Paul when he wrote to the church in Thessolonica said in 1 Thess. 1:5 "For our gospel did not come to you in word only, but also in power and in the Holy Spirit and in much assurance. Isaiah 54:11 tells us that the Lord's word will not return void and will accomplish what He pleases. Therefore, with such precious promises, gospel tracts are a great way to spread the good news of the gospel.
There are numerous ways in which you can use gospel tracts such as; leaving them in public bathrooms, enclosing them in your bills, leaving them at residences doors who are not home, etc..They are a great way to get the word of God in many people's hands that you might not be able to visit with in regards to their salvation. In America, so many people are in a hurry it is often difficult to get them to stop for several minutes while you explain the great news of salvation. This is where tracts come in handy.
Also, they are a great way to start a conversation with someone about the things of God. You can kindly give them one, let them read it and ask what they thought and see where the conversation goes. I handed two young ladies tracts one time and they stopped right there on the spot and started to read them. As they finished reading them, they looked to me, and said if this is right, I'm not right with God. It was very powerful and sobering to them.
Tracts are also affective after you have been able to share Christ with someone. Afterwards, you can leave them with one that they can read and further dwell on. In any event use tracts because God uses them. I would recommend http://www.livingwaters.com/ , http://www.littleredbook.org/, www.mwtb.org , wwwtransfired.org for some solid gospel tracts with a clear presentation of God's way of salvation. May the Lord give you boldness and bless your efforts.