This is a very complex area, but I can give you one easy 'hack' which will help 90% of the time and prevent you making too many mistakes. Here it is: 1. There is only one situation where the present perfect is absolutely essential. This when we use 'since + [point in time] or 'for' + [period of time] to describe a situation or state which began in the past and is still continuing. For example, ''I've lived in this town since 2005', 'I've been married for 10 years' or 'I've known John since I was a child'. You have to use a present perfect in these cases. 2. In all other cases, if you are unsure whether to use a present perfect or a past simple, you should use a past simple. This is because there are many cases where a present perfect would be wrong, but there are relatively few cases where a past simple would be wrong. Even with the adverbs which traditionally signal a present perfect (already, yet, lately, recently), you can usually get away with using a past simple, and it won't sound too bad. That's the simplest advice I can give you.

Think of present perfect as a 'bridge' that connects the past with the present. It is most often used to refer to past actions that have no definite time frame. My students usually *click* onto the differences when I tell them that: a) Past simple is for FINISHED past actions. We know exactly WHEN it happened. Example: I MET my friends in town LAST NIGHT. b) if I were to use present perfect I could say something like I HAVE MET him BEFORE. This meaning is different. It means I met him sometime in the past but I don't say exactly when. I also tell my students how useful time references are for helping you to identify the right tense in exams or for helping you to speak correctly and fluently. a) For finished past actions - past simple: Yesterday, last night, last week, last year, ten years ago, a minute ago, a second ago ....etc. What do these time references all have in common? Answer: they refer to SPECIFIC times in the past. b) Present perfect: just, before, never, ever, recently, lately, for, since, etc. Examples: I have JUST finished my assignment. ( We understand that he/she finished it in the recent past - but we don't know EXACTLY when.) Another example: I have never seen him before. So, the first steps for you in clarifying when to use past simple and when to use present perfect are: 1) understanding the basic usages as explained above. 2) learning how to use the time references in sentences - for example, how we use 'since' and 'for' needs some understanding and practice. 3) Practise by using interactive quizzes online and speaking to a teacher of your choice till it *clicks*. You know you have mastered a grammar point when you can express yourself easily without over-thinking the point. It should just flow easily. This is why speaking practise and games are so important. Grammar exercise alone are not enough. Many students *know* grammar rules off by heart but still can't speak fluently.

For my case I am distinguishing it to have effect and time If the effect is visible at the present then it's a present perfect tense: "You've changed so much over the years" or "You haven't changed a bit" IF the action has specified past time, then it is a past simple tense "Yesterday, I painted my walls" but no time specified should be "I've painted my walls" Though, I'd say you cannot have everything nicely, even I have some rules mixed up I think... The problem is, I might get it within reading something but not make rules. I tried my best summing it up but do not depend on my source. :(

All Perfect tenses express actions which happen before another action or point in time. Past Perfect is something that happened before Past Simple: "By the time my mum came (Past Simple) home I had done (Past Perfect) the dishes." This context doesn't always come in the same sentence, can be for instance 2 different sentences with common context. And Present perfect is something that happened "up to now": "I've graduated from university." (up to now, as nothing else is stated) but "I graduated from university last year." (Last year make the whole difference)