I agree with everything iCake wrote.
Just want to add some thought on "ещё".

At the first glance, it may seem too complicated for it has so many meanings and different ways of being translated into English (still, else, yet, more, also...). However, I'd like to offer some advice:

1. You are not required to learn all its usages at once. I think it would be much easier if you learn the ways it is used step by step.
2. However, there is something which makes us, native speakers, think it is the same word. It is better not just to learn all its special meanings (which might seem unrelated), but to grasp the basic idea what it has in common in all those usages.

My opinion is that the main idea of "ещё" is addition or continuation. Even the addition can be thought of as a continuation of a list (when you add an item to a list of items, you continue the list). I will try to apply this concept to all iCake's examples.

Quote Originally Posted by iCake View Post
Let's First, shows that the action is already started but still is in process, in other words it's not finished. It works as YET for negatives or STILL for positives in English. Examples:

Я ещё живу в России - I still live in Russia
- I continue living in Russia.
Quote Originally Posted by iCake
Я ещё не выкурил сигарету - I haven't smoked the cigarrete yet
The cigarette continues being not smoked to the end. Imagine it in the time scale: Я не выкурил (it assumes I am in the process of smoking, but did not finish it) - Я не выкурил - Я не выкурил - Я ещё не выкурил (this state still continues).

Quote Originally Posted by iCake
The second sense of ещё is the unique sense of также. Examples:
Он был умным. Ещё он был сильным - He was smart. Also, he was strong.
- He was smart. To continue (describing him), he was strong.
Quote Originally Posted by iCake
Он студент, но он ещё семьянин - He's a student, but he's also a family man.
- He's a student, but to continue (describing him) he's a family man.

Quote Originally Posted by iCake
The third sense is adding more of something to something or again.

Here we go explaing the previous example:
Я ещё поживу в России - that means that you had lived in Russia and will live in Russia again
- I will continue my experiences of living in Russia (this time is not the last time, it is to be continued).
Quote Originally Posted by iCake
Мне нужно ещё 10 долларов - I need ten more dollars.
- It assumes I have some money already, but it is not enough. So, I need you to continue supplying me with money.

Actually, this sense is very common, you can learn it from some short expressions like "кто-то ещё" (someone else), "что-то ещё" (something else), "где-то ещё" (somewhere else), "ещё один час" (one hour more), "ещё два стакана" (to glasses more) etc. It means addition, but as I wrote above, addition IS continuation.

Quote Originally Posted by iCake
The fourth and last sense I want to explain is showing that you didn't start an action yet. Used in negatives with imperfective verbs:

Я еще не курил сигарету - I haven't started to smoke the cigarette.
- "Я не курил сигарету" implies the action has never started. And this state continues up to the present moment (and maybe more). Again, imagine it in the time scale: Я не курил (I did not smoke = never started smoking it) - Я не курил - Я не курил - Я ещё не курил (this state still continues).