After a historic 1,200-point rally last week, investors and traders alike should approach this week with caution.Value plus snapback potential equals opportunity. Every week, I share my snapback ideas with TheStreet.com readers through my Rocket Stocks portfolio at Stockpickr.com. Today, for RealMoney subscribers, I'm giving a preview of next week's picks and recapping how last week's stocks fared. First, a quick recap: Arch Coal ( ACI): Up 20% on the week after its third-quarter earnings more than tripled, beating the Street's expectations. Arch Coal reported net income of $97.8 million, or 68 cents per share, compared with $27.2 million, or 19 cents per share, a year ago. CF Industries Holdings ( CF): Up 40% despite its third-quarter profits falling as it recorded higher unrealized losses on its natural gas hedges. Still, sales rose 75% to $1.02 billion, the result of substantial price increases for all of CF's fertilizes BioMarin ( BMRN): Up 10% on the week after swinging to a third-quarter profit and reaffirming its outlook for a profitable 2008. Valero Energy ( VLO): Up 15% despite having its third-quarter profit fall by more than 9% from a year ago. Net income for the quarter went to $1.15 billion, or $2.18 a share, down from $1.27 billion, or $2.09 a share, a year ago. Blackboard ( BBBB): Down 25% after giving a bleak outlook for the rest of the year. Cliffs Natural Resources ( CLF): Up 15% even after CEO Joe Carrabba said that he sees a protracted recession in 2009. He also said: "We have not changed our view of the growth of the steel industry. We believe a super-cycle is here and we are just in a hiccup at the moment."