A little bit
Use this for 'a tiny bit' or to sound friendlier. It's the diminutive of 'un poco' and is extremely common in casual conversation.
Means 'some of' or 'a bit of'. Use this before a noun, like 'algo de azúcar' (a bit of sugar).
Literally 'a pinch of'. Use for small amounts of uncountable things like spices, salt, or even abstract concepts like luck.
Do you speak Spanish? — Yes, I speak a little bit.
I'm a little bit tired today.
Do you want more cake? — Just a tiny bit, please.
The soup needs a bit of salt.
'Un poco' and 'un poquito' are universally understood and used everywhere. 'Un poquito' is often preferred in casual speech to sound softer or friendlier.
'Un tantito' is a very common colloquialism meaning 'a little bit' or 'just a moment'. For example, 'Espérame tantito' (Wait for me a little bit).
In addition to 'un poquito', you'll hear 'un tris' to mean a very tiny amount. '¿Le pongo azúcar? — Sí, un tris'.
'Un chin' is the most common way to say 'a tiny bit' in colloquial speech. It's used constantly.
'Un poco' is standard. The more colorful Latin American variations like 'un chin' or 'un tris' are not used.
Using 'un pequeño' for 'a little bit'. For example: *'Hablo un pequeño español.'* — 'Pequeño' means 'small' in size. For quantity, always use 'un poco'. The correct sentence is 'Hablo un poco de español'.
Confusing 'poco' and 'un poco'. — 'Poco' alone means 'little' or 'not much' and has a negative feel ('Tengo poco tiempo' means I have little time, and it's a problem). 'Un poco' means 'a little bit' or 'some' and is neutral or positive ('Tengo un poco de tiempo' means I have some time available).
Incorrectly matching gender with 'un poco de'. For example: *'Quiero una poca de agua.'* — The phrase 'un poco de' is fixed. It does not change for gender. It's always 'un poco de' followed by the noun. The correct sentence is 'Quiero un poco de agua'.