The Parable of the Sower
1That same day Jesus went out of the house and sat by the lake. 2Such large crowds gathered around him that he got into a boat and sat in it, while all the people stood on the shore. 3Then he told them many things in parables, saying: "A farmer went out to sow his seed. 4As he was scattering the seed, some fell along the path, and the birds came and ate it up. 5Some fell on rocky places, where it did not have much soil. It sprang up quickly, because the soil was shallow. 6But when the sun came up, the plants were scorched, and they withered because they had no root. 7Other seed fell among thorns, which grew up and choked the plants. 8Still other seed fell on good soil, where it produced a cropa hundred, sixty or thirty times what was sown. 9He who has ears, let him hear."
10The disciples came to him and asked, "Why do you speak to the people in parables?"
11He replied, "The knowledge of the secrets of the kingdom of heaven has been given to you, but not to them. 12Whoever has will be given more, and he will have an abundance. Whoever does not have, even what he has will be taken from him. 13This is why I speak to them in parables:
"Though seeing, they do not see;
though hearing, they do not hear or understand. 14In them is fulfilled the prophecy of Isaiah:
" 'You will be ever hearing but never understanding;
you will be ever seeing but never perceiving.
15For this people's heart has become calloused;
they hardly hear with their ears,
and they have closed their eyes.
Otherwise they might see with their eyes,
hear with their ears,
understand with their hearts
and turn, and I would heal them.'[a] 16But blessed are your eyes because they see, and your ears because they hear. 17For I tell you the truth, many prophets and righteous men longed to see what you see but did not see it, and to hear what you hear but did not hear it.
18"Listen then to what the parable of the sower means: 19When anyone hears the message about the kingdom and does not understand it, the evil one comes and snatches away what was sown in his heart. This is the seed sown along the path. 20The one who received the seed that fell on rocky places is the man who hears the word and at once receives it with joy. 21But since he has no root, he lasts only a short time. When trouble or persecution comes because of the word, he quickly falls away. 22The one who received the seed that fell among the thorns is the man who hears the word, but the worries of this life and the deceitfulness of wealth choke it, making it unfruitful. 23But the one who received the seed that fell on good soil is the man who hears the word and understands it. He produces a crop, yielding a hundred, sixty or thirty times what was sown."
I just became a Christian today, and it's only very gradually dawning on me how huge a step this is. I don't particularly feel any different though, and there's a nagging in the back of my mind about whether I was really sincere in this. Also, any advice on what to do now? Obviously pray and read the Bible, but any books/verses in particular? Or anything else? 
Adding to what others have said I repeat that getting into bible study is a must. Also finding a place to worship (unless you already have) and fellowship with other Christians. Pray every day and that means just praising and thanking God for what He has done, is doing, and will do in your life. And talk to Him the way you would a friend. He listens. 
