We must hunt down and kill whoever thinks this stuff up...

present tense - lay
past tense - laid
past participle - laid

present tense - lie
past tense - lay
past participle - lain

I lay the pencil on the bed. I lie down on the bed.
I laid the pencil on the bed. I lay awake on the bed.
I have laid the pencil on the bed. I have lain on the bed all day.

And let's not forget go, went, gone. Go is present tense. Went is past tense. Gone is the past participle. No wonder kids hate school.

And why are men blond but women are blonde?