Reflexive Verbs: When to put se in front/behind dormir and reír?
I have the two verbs reír(se) and dormir, and don't know when I need to put in the se or me or le or any of that.
When would I just write dormir (to sleep) or dormirse?
Or reír (to laugh) or reírse?
I am really confused!
4 Answers
In the case of "dormir" (to sleep) versus "dormirse" (to fall asleep), it depends on what you mean. Here are the meanings with example sentences from my Gran Diccionario Oxford:
dormir, verbo intransitivo to sleep;
¡Niños, a dormir! = It's time for bed, children!
No dormí nada. = I didn't sleep a wink.
Necesito dormir ocho horas. = I need eight hours' sleep.
No me deja dormir (en or (Esp) por la noche) = It keeps me awake at night.
Dormimos en un hotel. = We spent the night in a hotel.
Durmió de un tirón. = She slept right through (the night);
Se fue a dormir temprano. = He went off to bed early, he had an early night.
dormir a pierna suelta (fam) to sleep the sleep of the dead
dormir como un lirón or un tronco or un bendito = to sleep like a log (colloq)
You can also use "dormir" as a transitive verb.
a) (hacer dormir):
Durmió al niño. She got the baby off to sleep.
Sus clases me duermen. = His classes send o put me to sleep.
dormir la mona or dormirla (fam) to sleep it off (colloq)
b) (anestesiar) to give … a general anesthetic, to put … out (colloq);
Todavía tengo este lado dormido. = This side is still numb.
c) dormir la siesta to have a siesta o nap
Have a look here at the site (the dictionary tab) to see similar sentences for the verb "to fall asleep" ...dormirse.
Reír is just the to laugh, without further implications. It is more used in literary Spanish.
Reírse is the same, but it is used for spontaneous laughters, when you are laughing at someone or something (reírse de).
Janice's post is right on, but I suggest you read about "verbos reflexivos", and "verbos pronominales" to get the full picture. Otherwise you are probably going to think that this is a clever plot aimed to confuse prospective Spanish learners 
A reflexive pronown is only placed after an infinitive or a gerund form of the verb. Ex, dormirse, durmiendose, or before a conjugated verb. Ex, me río de ti. Me levanto. etc. Le isn't a reflexive pronown. Only me, se, and nos. So you can say: Estoy levantándome (note the accent) or estoy riéndome de ti (note the accent). So you can pick either the end of an infinitive or gerund, or before the conjugated verb. Spanish is chock full of those nasty little reflexive verbs that have different meanings than the same verb when it's not reflexive. You've got no choice but to deal with it. It's not like English at all and doesn't translate word for word at all.
