Start with the essentials, in order
Guest of honor, occasion, date, time, place, then an RSVP line with a reply-by date — that's the whole skeleton, and it's all most invitations need. Keep the essentials in that order and keep them scannable; anything extra (parking, dress code, 'no gifts, please') belongs in a smaller note at the bottom so it never crowds out the five things people actually need to show up.
Let the opening line set the tone
The first line decides whether the invitation feels formal, warm, or cheeky before anyone reads a detail. 'Please join us to celebrate Daniel's birthday' is timeless; 'It's Daniel's birthday and we're making a night of it' is relaxed and fun. Match the register to the actual party — a rooftop dinner and a backyard cookout should not open with the same words.
Add the extras only if they matter
Dress code, whether kids are welcome, a gift note, or a theme are worth including only when they change what a guest does — otherwise they're clutter. If you'd genuinely rather not receive presents, 'your company is the only gift we need' says it gracefully; if there's a theme, name it plainly ('come in your best '70s') so no one has to guess.