Tip #16 - Crying during dua.
One of the ways in which sincerity is shown in dua is through crying. This brings about a feeling of humility and helplessness in front of Allah and shows the importance and seriousness of your request.
The Prophet (peace be upon him) once said, 'O Allah! My ummah (nation)! My ummah!' and he started crying. Allah said to the angel Jibreel, 'O Jibreel, go to Muhammad, and your Lord knows - and ask him what makes him cry?' So Jibreel went to the Prophet and asked him. The Prophet, responded that he was crying out of concern for his followers, just like Ibrahim and Isa were concerned for their followers, and Allah knew why he was crying, without having to ask Jibreel. So Allah said, 'O Jibreel! Go to Muhammad and say, 'we will please you regarding your followers, and will not cause you grief.'' [Reference: Sahih Muslim]
The above is a very special instance, where Allah almighty did not just answer the Prophet's dua, but sent angel Jibreel to console him. This is an example of the swift response of Allah to the one who calls on him with sincere tears in his eyes.