All you have to do to get the 2nd course is get a perfect score on the 1st course when you finish your game and should say you can now play on the 2nd course of mini-golf! It doesn't matter what character you use but you have to be in one player mode without any computer players.
When you use a certain player or caddy many times, you will build loyalty for that character. However, this loyalty is only useful in tournament mode. Choose your characters wisely.
Notice how your caddy is on the fairway and not next to you sometimes. When you notice your caddy is not next to you, scan down the fairway. Wherever your caddy is standing, this is a signal for a "safe shot". Aim for your caddy to avoid water or sand traps. However, this will happen only once a hole and not on every hole.
To unlock extra outfits play as the same character four times in tournament or verus mode, this will then also unlock outfits for you to buy in the shop. Note: The extra outfits unlocked in the shop can be won by beating the character in HARD VS mode. It will also be cheaper as most characters can be beaten by using 2-4 pitch hit coupons while outfits to be bought range from 5000 - 15000 points