Title. John the Baptist came to clear the way. Preparation for ministry: baptism, temptation.
A. 1:1–13 Preparation
The gospel is announced (1). This is all part of the plan, and John the Baptist comes to prepare people (3). John points to the Spirit-anointed one to follow (8) ["Christ"=anointed one]. Jesus himself comes, but has his ministry affirmed by God (11) and is prepared in the wilderness (13) before he begins.
Things to talk about
1 Rico suggested three points to draw out:  The gospel is the best news;  It is all about Jesus;  Jesus' identity is the Son of God.
4 We have a precursor to Jesus' ministry. How do we expect Jesus to want people to respond if John asks for repentance, and people need forgiveness for their sins?
9 came from Nazareth What impression does this sort of detail at the start of a book seek to give about the sort of narrative which is coming up?
10 Ask questions to draw out:  Jesus deliberately includes himself with the sinners being baptised here (check out Is 53:12);  He is now the anointed one;  He is the Son. These are the same three statements as in 1. What has Jesus done that he is already beloved? What does this tell us about Jesus that he can have this sort of relationship with the Father?
13 Why does Mark not say whether Jesus or Satan won?
2–3 These verses are very hard to explain, especially if you try and look up the OT reference. 2 is from the Greek version of Ex. 23:20, and Mal. 3:1; 3 is from Is. 40:3. Mark is weaving together several strands of OT thought to do with God preparing his people for entrance into the kingdom (Ex.) or restoration of it (Is.). He is also picking up on the last OT prophecy chronologically (Mal.), but puts a fresh twist on it: in these sorts of composite quotations in the NT the general context (flow) and immediate phrases from the passages are being directly referenced, so Mark is unambiguously saying that the "Lord whom you seek [has] suddenly come to his temple"—in other words, referencing Jesus as the LORD. These sorts of complex quotations are hard work to explain, so perhaps just focus on the Mal. and praise God for the long time he patiently endured while bringing his plan for salvation to fruition.
5 Baptism was normally reserved for gentile converts; this is new to proclaim that all, including Jews, are unclean and need purification.
6 Elijah wore similar clothes in II Ki. 1:8, so Mal. 4:5 is a probably reference.
10 Again, a direct prophetic reference to the few prophets who saw heaven in this way. The Trinity is worth exploring here too, as the distinctive persons are already dramatically coming into play in a way they have not during thousands of years of OT history, simply in the new personal relations brought about by Jesus' coming.
13 See Moses' forty days. Is Jesus or Satan being tested? Jesus knew who he was, but manifested his glory as the perfect prophet.
 arrested John sets the pattern for Jesus' ministry to follow too.
Questions for ourselves
3 "Be comforted, my people." Pray to God that we would think of this news and be comforted by it (comfort is the Lord's to give, not for us to concoct).
9 So why was Jesus baptised?
13 Did Jesus enjoy willingly submitting himself to disciplines and devotions to God, and should we?