Though you may already know that lay is correct in both of the following sentences:

1. Everyday I lay my towel in the shade on the beach.
2. Yesterday I lay down in the shade on the beach.

You might not be aware that the following sentences are the equivalents after the tenses have been adjusted:

1. Yesterday I laid my towel in the shade on the beach.
2. Everyday I lie down in the shade on the beach.

Confused? well check out this cool site I just discovered!

Here are a few screen caps to give you an idea of what to expect!

and for the pesky group of conjunctive adverbs:

So, make good use of this site; after all, everyone gets confused about some expressions every now and and again.