What's par for the course - in attire, that is
Whether the courses you frequent are public or private, rules are rules. Don't assume, just because you're playing on a public course, that you can show up in jeans and a T-shirt.
What's appropriate to wear:
Shirt: A golf shirt is perfect. You know the kind- a pullover shirt with a collar and short sleeves. Usually, golf shirts will be a little longer than an ordinary polo shirt, to help them stay tucked in even after repeatedly swinging at the ball. Avoid loud, splashy patterns. Keeping your look understated with keep the focus on you rather than on your clothing.
Pants, Skirts, Skorts, and Culottes: Pants always will do very nicely - linen, khaki, cotton, or, in cold weather, wool. Unless you know they're acceptable, avoid jeans. For women, capri pants, a skirt, a skort (shorts made to look like a skirt by having a panel across the front and back), or culottes also work nicely.
Shorts: Particularly Bermuda-length shorts are appropriate virtually everywhere these days, especially in warm weather. Avoid gym shorts, short shorts, or cutoffs.
Shoes: Golf shoes, if you have them, are perfect. Most clubs now require soft spikes rather than metal ones. Your best bet is to buy a good pair of soft-spike golf shoes; then you won't have a problem at any venue. Do not get caught with metal spikes on a soft spike facility - you may be asked to stop playing.
If you don't have golf shoes a good pair of sneakers will do in a pinch. Avoid wearing street shoes with a heel because the heel could make an impression in the green and cause a mark that could throw a putt off-line.
Cool-Weather Clothes: If you play on a day that's cool or even downright cold, be prepared to layer with a sweater, Windbreaker, and/or fleece vest or jacket, as well as any other cold-weather attire that you personally favor. When it drops below fifty degrees in Vermont, I'll still play quite happily wearing the long underwear and hat that I also use for skiing!
Rainy-Weather Clothes: While a heavy downpour might drive you from a course, be prepared to weather a little light rain. Pants and jackets now come in water-resistant materials such as Gore-Tex that will keep you dry, but that also breathe and are supple enough to let you swing a club comfortably. Bottom line: if the forecast predicts rain, come prepared for the worst.
The Ubiquitous Golf Hat: When to doff it and when to leave it on? The pros must get coaching on this because they invariably handle it so gracefully. As they walk up to the eighteenth green on Sunday, they acknowledge the gallery's applause with a gracious tip of the hat. When the match is over, they never fail to take off their hats as they shake each other's hands. Nice tradition - a real show of respect.
What should the rest of us do? Most assuredly, when you're in a club's dining room, follow the house rules. Many clubs have a hats-off policy indoors. It's a small gesture of respect that, much like the game we all love, is steeped in tradition that goes back literally hundreds of years.