Two verbs that give many native speakers fits are to lay and to lie.
Remember that lay is transitive and lie is intransitive. This post focuses on mistaken spellings of the past tense forms of lay and lie.
The principal tenses of lay (to place) are lay, laid, (has) laid:
Please lay the books on the table in my office. (present)
We laid the key on the counter. (simple past)
You have laid the wrong pattern on the worktable. (past perfect)
The principal tenses of lie (to recline) are lie, lay, (has) lain.
Lie down, Fido. (present)
He lay in bed all day. (simple past)
He has lain there long enough. (past perfect)
Here are some typical errors: