Learning how to choose tropical fruits

Since we've moved to Singapore we've been buying regional fruits: watermelon, mango, melon, etc.
However I haven't been always successful at picking them. Sometimes they are great, sometimes they are not ready.
Before my next shopping, I've searched the web for advice.
Here is what I found.

For watermelon, which is pretty consistent across sites:
1. LOOK – Your watermelon should be firm, symmetrical and free of major bruises or scars. Some minor scratches are okay, however. After all, the purpose of that thick rind is to protect the delicious contents inside. Ripe watermelons should also be dark green in color.
2. LIFT – The ripest watermelons have the most water. And since watermelons are 92 percent water, your watermelon should be relatively heavy for its size.
3. TURN – Turn your watermelon over and check out its bottom, which should have a creamy yellow spot (also called “the ground spot”). This is where the watermelon sat on the ground while it soaked up the sun at the farm. If this spot is white or greenish, your watermelon may have been picked too soon and might not be as ripe as it should be.

For mango, it's not as clear so I will try the following:
1) Touch and feel around the entire mango. Ripe mangoes will be slightly soft to the touch just like avocados and peaches, but not soft or mushy enough to where your fingers sink into or through the skin. On the other hand, if you do not plan on eating the mango for a few days, you may want to choose a mango with firmer skin.
2) Inspect the mango visually. Choose mangoes that are full, plump and round, especially around the stem because they will be the ripest and of the best quality. Choosing mangoes shaped like footballs are also ideal. Sometimes ripe mangoes will have brown spots or speckles; this is completely normal. Do not pick flat or thin mangoes because they are likely to be stringy. Avoid choosing mangoes with wrinkled or shriveled skin because they will no longer be ripe.
3) Smell mangoes near their stems. Ripe mangoes will always have a strong, sweet, fragrant and fruity aroma around the stem. Stay away from mangoes that smell sour or like alcohol because these mangoes may be overripe. Since mangoes have a high natural sugar content, they will ferment naturally, so the sour, alcoholic odor is a distinctive sign that the mango is no longer ripe.

Now, let's cross fingers that the above is working. I'll find out next weekend.