1. Explain it simply
Put 得 right after the verb, then an adjective: 他说得很好 (he speaks very well).
With an object, repeat the verb: S + V + O + V + 得 + adj, as in 姐姐唱歌唱得不错. The object can never come after 得.
Negate the adjective, not the verb: V + 得 + 不 + adj, as in 他跑得不快 (never 他不跑得快).
Ask with the adjective's positive-negative form: V + 得 + adj + 不 + adj, as in 他说得好不好？
2. Show examples
他说得很好。
Tā shuō de hěn hǎo.
He speaks very well.
V + 得 + adj
姐姐唱歌唱得不错。
Jiějie chànggē chàng de bùcuò.
Sandhi:Jiějie chànggē chàng de búcuò.
Older sister sings quite well.
repeat the verb after the object
他跑得不快。
Tā pǎo de bù kuài.
Sandhi:Tā pǎo de bú kuài.
He doesn't run fast.
negative: 得 + 不 + adj
你写汉字写得好不好？
Nǐ xiě Hànzì xiě de hǎo bù hǎo?
Sandhi:Nǐ xiě Hànzì xiě de hǎo bu hǎo?
Do you write Chinese characters well or not?
question: adj + 不 + adj
3. Share a tip
Keep 得 glued to the verb, and put the object before the second verb (说汉语说得好), never after 得. To say something is done poorly, negate the adjective (说得不好), not the verb.