Typically, a male turtle will be more colorful and more outgoing than a female.   Males have a flat or concave plastron (bottom shell), and females have a flat or convex plastron, which allows more space for eggs. Females will also almost always be larger.  Among water turtles, size is also a good indicator:  males are smaller than their female counterparts.  Also, male sliders have long claws on their front legs. When it comes to box turtles, males generally have bigger, fatter tails, and a vent (cloaca) that's further from the shell than the female's. Turtles are not able to breed until they've reached sexual maturity.  When it comes to water turtles, males should be at least three years old, and females need to be about five years old.  Neither male nor female box turtles will breed before they're at least five years old. Don't plan to breed a recently acquired turtle.  Wait at least a year. To increase the chances for successful breeding, it's suggested that you cool your turtles.  Nesting season can run from March through June, so the cooling period actually needs to take place January into February for water turtles and December through February for box turtles.  Keep turtles at a temperature between 50 and 60 degrees Fahrenheit for six to eight weeks for water turtles and eight to 12 weeks for box turtles. Leave the turtles alone during this period.  You can make food available, but they'll eat little or nothing at all. If your turtles live in an outdoor pond, you can take advantage of the natural cooling that wintertime offers and allow them to hibernate. After the cooling period has ended, return your turtles' habitat to its regular temperature. It's particularly important that your turtles eat well during the breeding season.  In addition to their regular diet, be sure the females get enough calcium and Vitamin D3.  A healthy diet for a water turtle will contain some combination of:  earthworms, snails, well-washed butter lettuce, melon, bananas, strawberries, blueberries, vegetable scraps, peas,...

TL;DR in Chinese:
首先你要有一只雄性和一只雌性海龟。 确保你的海龟性发育成熟。 冷却你的海龟。 好好地喂养你的海龟。