There are many situations at a wedding or bridal shower where you want or need to receive certain gifts from your guests and aren't sure the appropriate way to ask.. here are my suggestions:
"I live in a different state than where my bridal shower is being thrown. How do I let my guests know that gift cards are preferred?"
Even though bridal showers are all about showering the bride, sometimes that's not always possible. I personally don't think its rude to ask for gift cards.
*Put "gift cards are preferred" on the bottom of the invitation.
*Tell guests by word of mouth you are registered somewhere and you'd prefer to have your items sent to your house, not brought to the shower.
"My fiance' and I already live together and have everything we need, what do I register for?"
Think outside the box... register for fun things, ie: tools, baby room items, light bulbs, smoke detectors, batteries, toilet paper, cleaning supplies, etc. Everyone needs those items, even though they aren't exciting gifts, it'll be fun to have you guests watch you open all their silly items.
Create a honeymoon website. Guests can give you things specifically for your honeymoon, check out these sites...
"My fiance' and I will be moving after the wedding but we aren't sure where yet and we don't want to lug around or travel with all our gifts."
Put "Do to our living situation cash or gift cards are preferred." On the invites for your shower. Do not put anything on your wedding invites about preferred gifts it's just bad wedding etiquette, let word of mouth travel... if your guests know you, then they'll know the proper gift to give for your situation.