Present tense and present continuous ...

Present tense . 

subject	+	auxiliary verb	+	main verb
		do		base

There are three important exceptions:

1. For positive sentences, we do not normally use the auxiliary.
2. For the 3rd person singular (he, she, it), we add s to the main verb or es to the auxiliary.

Look at these examples with the main verb like:

	subject	auxiliary verb		main verb
+	I, you, we, they			like	coffee.
	He, she, it			likes	coffee.
-	I, you, we, they	do	not	like	coffee.
	He, she, it	does	not	like	coffee.
?	Do	I, you, we, they		like	coffee?
	Does	he, she, it		like	coffee?

Present tense .

The structure of the present continuous tense is:

subject	+	auxiliary verb	+	main verb
		be		base + ing

Look at these examples:

	subject	auxiliary verb		main verb
+	I	am		speaking	to you.
+	You	are		reading	this.
-	She	is	not	staying	in London.
-	We	are	not	playing	football.
?	Is	he		watching	TV?
?	Are	they		waiting	for John?

URL :

http://en.wikipedia.org/wiki/Present_tense

http://www.englishclub.com/grammar/verb-tenses_present.htm

http://www.englishpage.com/verbpage/simplepresent.html

http://esl.about.com/od/grammarstructures/a/prescont.htm

http://www.englishclub.com/grammar/verb-tenses_present-continuous_s.htm

http://www.isabelperez.com/happy/tenses/present_cont.htm