Pensar (to think) is used in a variety of expressions.

Adivinar el pensamiento – to guess what someone is thinking //  Leer la mente is also used (to read someone’s mind)
Cuando menos lo piensa – when you are least expect it, something will happen
Cuando menos se piensa – same as the last one
Después de pensarlo – After thinking about it….
Dos cabezas piensan mejor que una – two heads are better than one
Los grandes pensadores – great minds (Einstein , etc.)
Pensador – a thinker
Pensamiento – a thought
Pensándolo bien – after thinking about it…
Pensante – thinking (adjective) // Una persona pensante – a person who thinks a lot or uses one’s mind
Pensar antes de actuar – think before you act
Pensar bien de alguien – to have a good opinion of someone
Pensar con el trasero – the think with one’s rear end
Pensar de – to think of (opinion) // Qué piensa usted de Obama? – What do you think of Obama?
Pensar en – to think about // En qué piensa usted? What are your thinking about?
Pensar en grande – think big
Pensar en pequeño – think small
Pensar mal de alguien – to think badly of someone
Pensarlo – to think about it  // Lo voy a pensar – I am going to think about it.
Pensarlo mejor – think it over
Pensativo – pensive
¿Quién pensó el plan? – Who thought up the plan?
Se le ve el pensamiento – you can see someone’s thoughts because they are bald
Sin pensarlo dos veces – to not think twice about doing something (not to hesitate)

Tiquismos of the week:

• Piensa el ladrón que todos son de su condición – Evildoers always think the worst of others. Another variation is Cada ladrón juzga por su condición
• Pensar en los los huevos de gallo – to be distracted
• Pensar que la luna es de queso – to deceive oneself
• Pensar que los perros están amarrrados con chorizo – same as the last one
• Pensar que no es más que soplar y hacer botellas – to imagine something is easy