(一):I have something to say.

我有话要说。

I have something to say.
我有话要说。
Sure. Go ahead please.
好的。请说。

I wish/want/would like to speak.

I'd like to present my idea/opinion.

(二):I'd like to put a question to the first speaker.

我想向第一个发言者提问。

I'd like to put a question to the first speaker.
我想向第一个发言者提问。
Please go ahead.
请讲。
I wish to speak to Mr. Chen.
我想和陈先生交流一下。
I've one more question.
我还有个问题。