How do you pronounce vowels that are together?

Question:

In Nihongo, some vowels put together make different sounds. Houkou for direction is pronounced ho-ko. But then in hai, the a+i sounds like the american letter I.
I think I'm getting close to good conclusions, but I would like to know when two vowels together make a different sound.
ください
どうも =^_^=

Answer:

yup you are right.

They generally follow the rule you have formed.

Other 2 vowel combinations I can think of are:

a+e as in まちがえ(machigae)
=>this is pretty straightforward, prounounced as ma-chi-ga-eh

and

o+o as in おおい(ooi)
=> pronounced as "ohhh E" (I don't quite know how to describe this)

another one is

i+i as in かわいい(kawaii)
=>pronounced as ka wa E--

Hope that helps. *actually google translate has pretty good pronunciation I,believe, not translation though, so you could type the words there if you don't know how to pronounce them and listen*

EDIT:
btw, it would be better if you use よろしくおねがいします。instead at the end of your post. =)

EDIT2:
Just thought of 2 more combination.

e+i as in よてい(yotei)
=>pronounced as "yo tear"

and

u+e as in うえ(ue)
=>pronounced as "oo eh"