One of the most important things I do each week to prepare to share the gospel is to study the scriptures every day. As missionaries, we get 1 hour to study from the scriptures, and it is awesome! Sometimes it can be hard to focus on studying the scriptures, but I know that if we try to have the Spirit with us as we are reading there is so much we can learn. In D&C it says "seek not to declare my word, but first seek to obtain my word, and then shall your tongue be loosed; then, if you desire, you shall have my Spirit and my word, yea, the power of God unto the convincing of men." If we want to teach the gospel to other people, we have to learn about the gospel for ourselves first, and not just learn about the gospel, but gain our own testimonies.
Another thing that I do each week to prepare to share the gospel is to take the sacrament. The sacrament has some amazing promises! We promise God that we will always remember, and try to follow Him. In return, He promises us that we will always have His spirit to be with us. Having the spirit with us is absolutely essential when we are sharing the gospel. The Spirit can help us know who to share the gospel with, He can help us know when to share the gospel, He can help us to have the courage to bear our testimonies, and He can bear witness of the truthfulness of what we are saying. It is pretty pointless to share the gospel if you don't have the Holy Ghost there to help you. Taking the sacrament each week can help us to qualify to have the Holy Ghost with us all day, every day!
Something else that I do each week to prepare to share the gospel is to pray, a lot. My companion and I usually pray at least 30 times every day! We don't always know the best way to share the gospel with the people around us, but Heavenly Father does! He knows His children, and He wants ALL of them to hear about the gospel. I know that if we will pray to have missionary opportunities, and the Lord will bless us with little things we can do everyday to share the gospel. Even if it is just a simple act of service.
Scripture study, sacrament, and prayer are so important! In order to share the gospel with other people, we ourselves have to be converted first. I know that if we will do the little things each week (prayer, church, and scripture study), we will strengthen our own testimonies, and then we will qualify for God's help as we look for opportunities to share the gospel.