A day at the beach can be a ton of fun and very relaxing. A trip poorly planed can ruin more than just the day if you forget something like sunscreen. As fun as a beach trip can be it will require a little bit of planning ahead.
Bring the right clothes. Bring that beautiful new swimsuit you have all picked out, but don't forget that extra set of clothes for the ride home. That way you can avoid being wet and sandy and you can go somewhere else after.
Protect yourself from the sun. Don't ruin the whole trip with a bad burn. Protecting your skin from the sun's rays will keep it looking younger and protect it against skin cancer.
Don't forget something to sit on. A big towel or fold up beach chairs are perfect. If you bring a towel to sit on, don't forget to keep it separate from the ones you dry off with.
Bring a first aid kit. Small first aid kits are cheap and fit easily into your beach bag. You hope no one gets hurt but it's always better to be safe than sorry.
Bring a water resistant or waterproof bag. You're going to need a place for your valuables to stay dry and out of the sand. I recommend something that's water resistant or waterproof for your electronics.