Don`t use it immediately

Like bro, it`s obvious, use it when you are at 60 or below health so they won`t suspect it.

Don`t go near the water.

Even when you are cloaked water particles will still appear, this applies to all invis watches too.

If it`s a 1v1, use it to reduce damage taken.

The Dead Ringer has damage reduction when you activate it so in 1v1 you could use that in your advantage.

Use a friendly disguise to get outside the base.

Use a disguise that`s the same color of your team so when they "kill" you they won`t suspect you are a spy and dead ringed.