How to use shall and should?

I think the should is suitable.Because should 主要解 應該.
我不應該接受他們的禮物嗎?
I think the shall is unsuitable.Because shall 主要解 建議.
建議我接受他們的禮物嗎?
We use shall to make suggestions.We do not change the verb after shall .
e.g. Shall we give this card to Dad?

We use should to talk about the correct things to do.We do not change the verb after should.
e.g. He should use less paper.

shall
1. (用於第一人稱,表示將來)將,會
I shall be thirty next year.
明年我就三十歲了。
2. (用在問句中表示徵求對方意見,主要用於第一,第三人稱)...好嗎?要不要...?
Shall we begin now?
我們現在開始好嗎?
Shall I wait outside?
我在外面等好嗎?
Shall I turn on the lights?
我開燈好嗎?
3. (用於陳述句中的第二,第三人稱,表示說話人的意圖,允諾,警告,命令,決心等)必須,應,可
You shall have it back next week.
下星期一定還你。
He shall stay in bed.
他必須躺在床上。
He says he won't go, but I say he shall.
他說他不去,但我說他必須去。
4. (用在條約,規章,法令等文件中表示義務或規定,一般用於第三人稱)應,必須
Intruders shall be punished.
非法闖入者將遭處罰。

should
1. (shall的過去式,表示過去將來)將
We hoped that we should be able to do that.
我們希望我們能這樣做。
2. (表示語氣較強的假設)萬一,竟然
If the car should break down on the way, you would have to walk back.
萬一汽車中途拋錨,你就得走回來。
3. (表示可能性,推測,推論或期待)可能,該
She should be here any minute.
她該馬上就到。
Dinner should be ready by now.
此刻晚飯應該做好了。
4. (表示義務,責任)應該,應當
You should do as she says.
你應當照她說的去做。
He should work harder.
他應該更加努力。
You should help your mother with the housework.
你應該幫你母親做家務。
5. (表示委婉,謙遜)可,倒
6. (表示感情,意志等)竟然會;應該
I'm sorry it should be this way.
很遺憾,事情竟會是這個樣子。
It's strange that he should be absent.
真奇怪,他竟會缺席。
You shouldn't have told him about it.
你不該把這件事告訴他的。
7. (表示建議,命令,決定等)應該,必須
Crime should be punished.
犯罪應受懲罰。
8. (表示目的)會,可以
He stood away so that we should enter the room first.
他讓開一步,讓我們先進屋。
9. (表示結果,意願等)就,該
10. (表示徵求同意等)可以,該
Who should I see about my schedule?
關於我的日程該和誰商討?

Should.
"I should not accept the gifts."

shall.because shall is present tence in the "shall".
And the "should" is the past tence in the "shall",but it is presnet.So,we have to use "shall" in this sentence.