The issue of Allah 'guides' and 'misguides' whom He wills can be explained as follows:
1. "Yet he who spends on others and is righteous and affirms goodness, We shall ease the way of fortune for him. But he who does not spend and is unconcerned and rejects goodness, for him We shall ease the way of adversity." (92: 5-10)
Note, the Arabic words used taysir (task made easier) and imhal (temporary relief allowed) respectively for the treatment meted out to the two categories of individuals.
God says that if you are really honest in doing good work, God will guide you to the right path. If you insists on doing bad things, despite the revelations that have come to you, then God will make misguidance easier for you.
2. For those who chose to purposely block the truth and prevents others from knowing the truth, God sealed their hearts (misguides them):
"When the hypocrites come to you, they say, 'We confirm that you are the messenger of Allah.' Allah indeed knows you are His messenger. Allah bears witness that hypocrites are indeed liars. They have made their oaths a shield, thus they obstruct others from the way of Allah. It is certainly evil what they do. That is because they came to believe, and then disbelieved, so their hearts were sealed and now they do not understand." (63:1-3)
and
"... raised a barrier in front of them and a barrier behind them, and have covered them over so that they are not able to see (the truth). Whether you warn them or do not warn them, it is all the same; they will not believe." (36:9-10)
3. The point is, everyone must make a choice. The Quran says:
"There is no compulsion in religion. Distinct is the way of guidance from error. He who turns away from the forces of evil and believes in Allah has grasped a firm handhold which will never break. Allah hears all and knows everything. Allah becomes the Protecting Friend of those who (want to) believe. He brings them out of darkness (of ignorance) into light (of truth). As for those who (want to) disbelieve, forces of evil are allowed to become their patrons. Such are rightful owners of fire. They will abide therein." (2:256-7)