Luke 8:4-15 When a great multitude came together, and people from every city were coming to him, he spoke by a parable.  "The farmer went out to sow his seed. As he sowed,
 

some fell along the road, and it was trampled under foot,

and the birds of the sky devoured it.

other seed fell on the rock, and as soon as it grew, it withered away,

because it had no moisture.

Other fell amid the thorns, and the thorns grew with it, and choked it.

Other fell into the good ground, and grew, and brought forth fruit one hundred times."

As he said these things, he called out, "He who has ears to hear, let him hear!"
Then his disciples asked him, "What does this parable mean?"
He said, "To you it is given to know the mysteries of the Kingdom of God, but to the rest in parables; that ‘seeing they may not see, and hearing they may not understand.’
Now the parable is this: The seed is the word of God.
 

Those along the road are those who hear, then the devil comes,

and takes away the word from their heart, that they may not believe and be saved.

Those on the rock are they who, when they hear, receive the word with joy

but these have no root, who believe for a while, then fall away in time of temptation.

That which fell among the thorns, these are those who have heard,

and as they go on their way they are choked with cares, riches,
and pleasures of life, and bring no fruit to maturity.

That in the good ground, these are such as in an honest and good heart,

having heard the word, hold it tightly, and bring forth fruit with patience. (web)

• Along the path: How does the devil take away the word from their hearts?
• Among the rocks: What do the rocks represent? Why do you suppose they fell away?
• Among the thorns: How do these things "choke" the Christian life? What are indications of maturity?
• On good soil: What are common characteristics between soil which is good from growing plants and those who not only receive the message well, but also produce fruitfulness after much perseverance?

Christians are called to be the farmers, sowing the seed of the Word of God into the world. Of course the farmer wants to sow his seed only a good ground so that it will be fruitful. And there are often things he can do to prepare the soil. But this is not soley his responsibility. As he sows seed, I would imagine he would focus on what he perceives is good soil. But in the process, the seed also lands in places where the soil is not ideal.
The ones along the path are those who fail to understand how the word applies to them. They don't take it to heart. Satan blinds their eyes to the truth, or puts mental stumbling blocks in their way. I'm always amazed when I hear someone from the intellectual elite say that Bible is difficult for them to understand. I think they must simply be reading it incorrectly. The Bible pretty much says what it means and means what it says. And thus people of all ages and generations have come to understand it. But there is a spiritual blindness that veils people's hearts. Speaking of the blindness of the Jews to the revelation of the Bible, Paul writes:

"But their minds were made dull, for to this day the same veil remains when the old covenant is read. It has not been removed, because only in Christ is it taken away. Even to this day when Moses is read, a veil covers their hearts. But whenever anyone turns to the Lord, the veil is taken away." 2Cor 3:14-16

Those on the rock must in humility break up their soil and remove the rocks. They must be willing to give up their former convictions which hinder them from believing. Or else others can pray for God to break up their soil by bringing them through humbling circumstances in hopes of developing in them the necessary humility to respond to the gospel properly.

Those among the thorns I think are among the redeemed. Their problem is not one of being alive, but being mature. The Matt and Mark passages also say that they are "unfruitful". One must be mature before one gets married and has children. So also in the Christian life, to be fruitful one's faith must be mature. However, this is not saying that such people produce no fruit at all, but rather the fruit they produce is an immature fruit, not worth picking. This is made clear in the Luke passage with the greek word "telesphoreo" meaning: to bring to (perfection or) maturity. This is not to be confused with the John 15:2 "He cuts off every branch in me that bears no fruit." or the parable of the barren fig tree (Lk 13:6-9), in which there is a complete absence of fruit. These later represent nominal Christians of a dead faith, as James writes: "faith by itself, if it is not accompanied by action, is dead." James 2:17 But these do not refer to those among the thorns. They do produce fruit, but immature.

What hindered their maturity was that they were growing in the midst of all kinds of concerns. And these concerns shaded them from the Son of God. They weren't getting sufficient light to grow to maturity. Furthermore, the plants around them were sucking the water out of the ground making it less available for them. The worries, riches and pleasures in life can suck the Christian life right out of us, leaving us drained, incapable of producing fruitfulness.

It doesn't take much ability or material things to be fruitful. It takes just five loaves and two fish. But we must, by faith, be drawing on the life of Christ free from distractions "casting all our anxiety on him." (1Pet 5:7) And we should view ourselves as soldiers and servants of Christ, no owning our own lives. "No one serving as a soldier gets involved in civilian affairs-- he wants to please his commanding officer." (2Ti 2:4) This is not to say that we live as monks, but to follow the examples of Jesus and Paul. For example Paul worked at a secular job, but it didn't define who he was. Similarly with respect to marriage. Raising a family can be like living among thorns. Paul writes:

"I would like you to be free from concern. An unmarried man is concerned about the Lord's affairs-- how he can please the Lord. But a married man is concerned about the affairs of this world-- how he can please his wife-- and his interests are divided. An unmarried woman or virgin is concerned about the Lord's affairs: Her aim is to be devoted to the Lord in both body and spirit. But a married woman is concerned about the affairs of this world-- how she can please her husband. I am saying this for your own good, not to restrict you, but that you may live in a right way in undivided devotion to the Lord." 1Cor 7:32-35

The seed on good ground are those who don't just simply understand the message, but receive it into their hearts and conform their life to it. This is not to say that they received it with a blind, gullible faith. But that they took it seriously. Consider the noble manner in which the Bereans received the message:

"Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true." Acts 17:11

"you know that the testing of your faith develops perseverance. Perseverance must finish its work so that you may be mature and complete, not lacking anything." James 1:3,4