Depending on what you're making, you might take a bit of juice from a jar of dill pickles. Otherwise, there really is nothing quite like dill.

Ditto to SKK. There is nothing like dill. So, pick something you like or just leave it out, and just know that you're creating something new.

There is nothing like dill. Depending on what you are making fennel seed and/or celery might work.

I'd say it depends on what you're making, but other fresh herbs could be used, like tarragon or basil. For dill seed, maybe celery seed or caraway. But I don't know of anything that really tastes like dill. Maybe a splash of 'pickle juice'?

What is it that you are making? I'd use different things, depending on the nature of the dish, the other ingredients/flavors, etc. ;o)