Can I talk to you for a minute?

Can I ask you something?

Do you mind if I ask you something?

I need to talk to you for a minute.

I have to tell you something.

There's something I need to tell you.

There's something I think you should know.

We need to talk.

Prefacing a negative subject

I don't mean to be rude, but . . .

I hate to tell you this, but . . .

I don't know how to tell you this, but . . .

You might not like what I have to say, but . . .

I wish I didn't have to tell you this, but . . .

This may be unpleasant, but . . .

This may seem blunt, but . . .