Saying it will happen: sẽ

Sẽ before a verb says something will happen: Em sẽ gọi lại cho anh. I'll call you back. It's close to English "will".

Like đã, it's often left out when a time word already says when: Tuần sau tôi về quê. I'm going back to my hometown next week. You can still add it, and many speakers do; it can stress that it will really happen, like a promise: Mai em sẽ trả tiền chị. I will pay you tomorrow.

"Won't" is sẽ không, with sẽ first: Tôi sẽ không nói với ai. I won't tell anyone.

To ask about the future, sẽ stays in its place and the question word goes where the answer will be: Anh sẽ ở Việt Nam bao lâu? How long will you stay in Vietnam?

For something about to happen any minute, use sắp instead: Xe sắp tới rồi. The car's almost here. Sắp means "soon" by itself, so it doesn't take a time word; sẽ can.

Keep sẽ for what will happen, not for asking someone to do something. English "Will you help me?" is a request; in Vietnamese that's Anh giúp em được không?