1. agree with用于以下用法：

①表示同意某人或某人的想法(即持同一观点),后面常接sb和what引导的句子：

I don’t agree with you. 我不同意你的意见。

I agree with what you say. 我同意你说的。

②表示“ (食物、天气、工作等)对…适宜”：

The dampness of the forest did not agree with him physically. 他的身体不能适应森林的潮湿。

I don't think the food here agrees with me.

我觉得这里的食物不对我的胃口。

③表示“与…一致”：

What he does does not agree with what he says. 他言行不一致。

2. agree to

①主要用来表示一方提出一项建议、安排、计划等，另一方同意协作：

They had little choice but to agree to his suggestion.

他们别无选择，只好接受他的提议。

Is he going to agree to our plan? 他会同意我们的计划吗？

②其后既可接动词原形 (此时to是不定式符号)，也可接动名词 (一般有逻辑主语，此时 to是介词)：

He agreed to go with us. 他同意和我们一起去。

I never agreed to lucy marrying him. 我从来没同意露西嫁给他。

3. agree on [upon]

主要指双方通过协商而取得一致意见或达成协议：

We agreed on the price. 我们就价格达成了一致意见。

Both sides agreed on these terms. 双方都同意这些条件。

注意：agree 不能接不定式的复合结构，所以汉语的“同意某人做某事”，不能直译为 agree sb to do sth, 而应根据情况改用其它结构：

　　他们同意我去。

　　正：They agreed to let me go.

　　正：They agreed to my going.

　　误：They agreed me to go.