How should I secure the drain hose to prevent it from coming off or leaking?

Wet the inside end of the drain hose with tap water (no other lubricant), squeeze the clamp ears open with pliers, and work the hose end onto the drain connector. Position the clamp over the area marked 'clamp' and release it so it sits 1/4 inch from the end of the drain hose. Do not force excess drain hose length down the standpipe, as this could cause siphoning. (Page 5)

From the official Whirlpool Thin Twin manual, page 5

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