someone please explain this grammar concept for me: Tenses

<p>for most of the grammar rules, i can understand it fine. it's just a matter of whether i can recognize it in a contex or not ( i know that's a pretty big thing). But for tenses, i simply don't understand them. i finally understood when to use past parfect and future parfect form, but when it comes to present perfect form, i get really confused. how do you know when you should use present perfect, or simple past, or even simple present? i checked many grammar books but they only tell me "use present parfect when something is in unspecific past or it still affects now." But that doesn't make much sense for me....my english teacher is not helping me very much either.</p>

<p>can someone please help me? i want to master this concept before june 4th test, since i seem to miss almost all the questions regarding tenses.</p>

<p>bumping the thread because i really need some help</p>