Since and for?

You can use google.com to find definitions for words like this: www.google.com/search?q=define+since

There will also be several dictionaries listed and you can look at those to find more examples, etymology, and other information. Etymology means the history of a word, like this: www.google.com/search?q=etymology+since

You need to read novels. Lots of novels. Any novels. Notice that they all have perfect spelling, perfect punctuation, perfect composition. Notice where they use one space and where they use two. Notice that every speaker in a dialog gets a new paragraph, and every paragraph is preceded by a blank line. Notice any writing techniques or figures of speech. Take notes so you know where you found what you know.