Tip #7 - Lack of hastiness.
Hastiness is a cause of your Dua being rejected Allah Almighty says, 'and man supplicates for evil as he supplicates for good, and man is ever hasty.' [17:11]
Abu Hurayrah narrated that the Prophet (peace be upon him) said, 'the dua of any worshiper will continue to be responded to, as long as he does not ask for a sin or breaking the ties of kinship, and as long as he is not hasty.' It was asked, 'O Messenger of Allah? And what does it mean to be hasty?' He responded, 'a worshiper says, ‘I have prayed and prayed, and I don’t see that it will be accepted’, so he gives up hope of being answered and leaves dua.' [Reference: Muslim, Sahih al-Jami: 7705]
To ‘give up’ means to turn away and break off from something, and the meaning intended here is that a person leaves Dua. This is what is meant in the following verse, 'they are not too proud to worship Him, nor do they weary.' [21:19]. This means that they do not stop worshiping Allah Ibn al-Qayyim mentions, 'and of the diseases that afflict Dua and prevent its response is that a person is hasty in expecting a response, and the response is delayed, so he gives up hope, and leaves Dua. His example is like that of a person who planted a seed, or a seedling, then guarded it, and took care of it, and watered it, but when it delayed in (giving its fruit) and reaching perfection, he left it and did not take care for it any more!' [Reference: Al-Jawab al-Kafi: p.10]
This does not mean that one should not pray that his Dua be answered quickly, as it was authentically narrated that when the Prophet (peace be upon him) prayed for rain, he said, '...quickly, and not delayed...' [Reference: Ibn Majah, al-Tahawi, al-Hakim, and others, from Ka'b ibn Murrah, as mentioned in Irwa al-Ghalil 2/145]
In summary, an important etiquette in getting your Duas answered is to persist in it and not being hasty and giving up on Allah.