The difference between 送 ,带 and 捎
【送】

一、Send something to somebody, this means You intentionally bring something to someone with your own payment, and this thing orignally belongs to you. This is usually used when you wanna go to pay a visit, or you wanna invite someone, to be in honor of something……ect.

E.g：


明天小明过生日了，我们送什么好呢？（Tomorrow is XiaoMing's birthday, what can we buy to send him as a present?）
今天是我们结婚的纪念日，我送你一枚戒指（I'd like to send you a ring for the anniversary of our wedding today.）


二、Can be also used you want to give someone something intentionally (for some special purpose, either good or bad).

E.g： 


我送她一束花，我爱她。(I sent her a bunch of flowers because of my love to
her).
我送领导1000元红包，希望仕途顺利( I sent my boss 1000 RMB for my future
official career).


三、 The way of "sending someone something" by using “送” NOT ONLY MEANS"Person To Person". But Just enpharsis "Something to the destination". So you can say：

我寄了它一个包裹，送他一个表. (I sent him a package with a watch inside).

【带】

Bring something to somebody. The way to "give someone something" MUST BE "Person To Person". And this usually has two meanings (either will be OK):


The object to be brought to others isn't yours.
Maybe you have a purpose to bring this thing to others, and this isn't your main aim. You just do it "buy the way" (=捎)


E.g:


今天小王生病了，请给他带作业本。(Please bring the workbook to XiaoWang, because he's ill today).
我去了一次南京，顺便给他带点好吃的东西. (I had a trip to Nanjig, and by the way, I brought him something good to eat).


【捎】

This word CAN BE ONLY USED wihtout any purposes, this means when you do something, you see that this could be also good/favourate to others. So you also do that "by the way"：

你既然要去看阿姨，我就不去了。顺便请捎给她我的问候，谢谢。

(Since you are going to your aunt's, Please bring my greetings to her as well and I won't go there. Thanks).

For “捎”，you can also say “捎带” instead.