One of the most important things you must learn about Czechs when you'll learning Czech is that when they say "no!", they mean "yeah!". They're usually nodding when saying that. However, it is not the only use of "no"...
No! Nono! No tak! Nebreč! (Come, come! Come on! Don't cry!)
No tak, pomož mi, prosím! (Come on, help me, please!)
No ne! No tohle! No tedy! Ty máš zase nový počítač?! (Wow! Goodness me! You have a new computer again?!)
replying by saying something that is obvious – no přece
Kolik je jedna plus jedna? – No přece dvě! (How much is one plus one? – Why, two. / Two, of course.)
COL.: so what? – no a?
Už ti nikdy neporadím! - No a? Stejně mi tvoje rada nepomohla! (I'll never give you any more advice! - So what? Your advice didn't help me anyway!)
No a ne? (Well, am I wrong?)
following up on the previous sentence
Potkal jsem kamaráda, zašli jsme na pivko... No, a najednou bylo ráno! (I met a friend, we went for a beer... Well, and suddendly it was morning!)