How can I master English's past tense?

1. note: usage does vary somewhat between UK English and American English dialects.

2. I walked. - simple past tense (simple here means: one, in this case, no helping verbs). Traditionally, its use is for describing events or states at a specific time in the past. Note that it is only used in affirmative statements, for all verbs except for forms of "to be". Did I walk? I didn't walk. (not: Walked I? not: I walked not. using "do" is the emphatic aspect of either the present or past tense. It is no longer grammatically "simple", because it's now a two word verb phrase)

3. I have walked. - present perfect. perfect - is an aspect added to a tense to express completion. Traditionally used either:

a. to express a state or event at no definite time in the past. It indicates the experience. I have walked (in the woods, on occasion).

b. to express that results of the past state/event are still true or recent. I have walked for two hours (and I'm still tired and haven't done any other walking since then).

4. I was walking. - present progressive/continuous. Prog./cont. is an aspect, added to the tense. It indicates that I am focusing on the past event/state in progress, either at one time or over a period of time as habitual events. It's like watching the video and reliving the moment, rather than merely noting it on a calendar (the simple past or past emphatic) or simply acknowledging the experience without specifying a time frame (the present perfect).

Often used to set up a scene, where other events or changes in state occur (using other past tense/aspect combinations).

5. I had been walking - past perfect progressive/continuous. perfect -- completed before another past event (because it's the past perfect and not the present perfect). continuous/progressive - in progress etc.

I had been walking for about thirty minutes when I realized I had forgotten to turn the stove off before leaving. (in this case, had been walking indicates that walking started in the past and continued for a period of time until "I realized", a single change in state at a specific time.)

6. All other past tense/aspect combos can be explained by understanding the meaning/use of the aspect term (prog./cont; perfect, emphatic/DO support). The neutral aspect is no aspect information, which only occurs twice in English: the simple present (I walk) or the simple past (I walked). "neutral" is not usually used, simple is used instead (but does not mean the opposite of complex)

7. American English allows the simple past to be a default tense, that can usually optionally replace any aspect combo. It is common for English speakers to use "I walked" even if I just sat down. A British speaker would likely use the more accurate: I have walked". Generally, the distinct uses of the past tense aspect combos are preserved in British dialects. American English doesn't have to use those other tenses, but often chooses to be more specific.

Of course ,there are many American and British dialects. Those are generalizations and not absolute rules.

"With difficulty" - given that many native speakers have strange ways when referring to the past!

If someone asks if you ever walked through the city say, "yes, I HAVE walked through the city"

If someone says "tell me a story", you say "On Monday I walked through the city and found a stray cat" or you can says "I was walking through the city and found a stray cat"

if someone asked "where were you?" you say "Oh, i was walking in the park"