One of the challenges of biblical interpretation is that some sentences–especially in Paul–can have so much information tightly packed into them. Skim the surface of them and you may have a general sense of what he’s saying, but God is in the details!
Here’s one suggestion. Try to put down on paper the various questions that the passage is answering. You might want to start with the standard questions (who, what, when, where, why, how).
Here’s one example: a single sentence from Romans 8:3-4:
By sending his own Son in the likeness of sinful flesh and for sin, he condemned sin in the flesh, in order that the righteous requirement of the law might be fulfilled in us, who walk not according to the flesh but according to the Spirit.
How do all these clauses relate to each other. Here are some questions you can ask to find out:
What did God do?
He condemned sin in the flesh.
(Note: this is why Rom. 8:1 — “no condemnation for those in Christ Jesus”–is true. God has to condemn sin; he will either condemn your sin, or he has already condemned your sin in the sacrifice of his Son. Unite with Jesus and condemnation is gone forever.)
How did God condemn sin in the flesh?
By sending his own Son [Jesus].
How did Jesus come?
In the likeness of sinful flesh.
Why (negatively) did Jesus come?
Why (positively) did Jesus come?
In order that the righteous requirement of the law might be fulfilled.
Who are we (negatively)?
Those who do not walk according to the flesh.
Who are we (positively)?
Those who walk according to the Spirit.