1. How to Increase and Decrease faith
Pondering the Merits of Islam and the Life of the Companions is a great source of Increase

2. Everything within the religion of Islaam is virtuous and good
Everything within the religion of Islaam is virtuous and good. Its beliefs are the most correct, truthful and beneficial. Its moral code and mannerisms are the most praise worthy and beautiful. Its actions and rulings are the finest and most just of all rulings and legislation.
With such significant observation and beautiful reflection over the fine qualities and advantages of this religion, Allaah adorns the eemaan in the heart of the servant and he makes it beloved to him. As Allah says in the Interpretation of the meaning:
"... but Allaah has made eemaan beloved to you and has adorned it in your hearts ..." [Soorah al-Hujurat (47):7]
Thus, eemaan in the heart becomes the most cherished and beautiful thing. .

3. As Ibn Qayyim Writes:
"If you reflect on the overwhelming and dazzling wisdom within this upright religion; this pure path and sharee’ah brought by the Prophet Muhammad of which no expression can contain its perfection, no depiction can grasp its beauty and nothing more superior can be thought up by the minds of the learned even if they were all to be collectively assembled into the mind of the most perfect of them.
It is enough in itself, that these integral and respectable minds have sensed the beauty of it and bear witness to its excellence and the fact that no other sharee’ah that has ever graced the world, is more complete, more sublime and greater. The Sharee'ah is itself the witness and the one borne witness to, it is the proof and the one used as proof and it is the claim and the evidence. Furthermore, if the Messenger had not brought any proof for it (i.e., its validity), it itself would be sufficient as proof, as a sign and witness that it is indeed from Allaah."

4. Consequently, contemplation over the merits and beauties of this religion, looking into the commands, prohibitions, legislation, rulings, moral code and etiquette that it has brought, is one of the greatest motives and incentives for one who does not yet possess belief in the religion, to embrace it and for the one who already has faith to attain an increase in it.
This is why Ibn al-Qayyim says: "The gist here, is that the distinct of this ummah and its learned; witness the beauty of this religion, its magnificence and perfection and when their intellects witnessed the ugliness of that which opposes it, its imperfection and illness, belief in this religion and love of it becomes fused with the delight of the hearts.”
A hadeeth related by Anas Ibn Maalik gives credit to what Ibn al-Qayyim mentions here. He reports:
"The Messenger of Allaah said, 'Three (qualities); whoever possesses them, will find the sweetness of eemaan: that Allaah and His Messenger are beloved to him more than anyone else, that he loves someone only for the sake of Allaah and that he hates to return to kufr just as he hates to be slung into the fire'." [Related by al-Bukhaaree]

5. Thus, this person who tasted the sweetness of faith; the delight of eemaan which has intermingled with the innermost of his heart; will not thereafter return back to kufr and deviation, following desires and false beliefs
Actually, he becomes amongst those who are the most firm in eemaan, the most adherent and stable and one who has the strongest attachment to his Lord and Creator.
This is because he embraced Islaam upon knowledge, conviction and understanding. He knew of the beauty of Islaam and its radiance, its splendor, purity and its distinction from all other religions. Hence, he was content with it as a religion and became very intimate to it, so how can he desire a substitute to it, seek to avert himself from it or wish to move on and make a change?

6. Amongst the benefits derived from this particular hadeeth is that it is regarded to be one of the many proofs of the Ahl as-Sunnah wa al-Jamaa'ah on the issue of the increase and decrease of eemaan and on the different levels of its people.
As one Scholar noted: From the fiqh of this hadeeth and the deductions made from it are..
"... within this hadeeth is an evidence for the varying levels of people with respect to eemaan and that it increases with obedience and decreases with disobedience because one who possesses all of these three qualities, finds the sweetness of eemaan in contrast to one who does not."

7. Another way of Increasing ones Faith
Is through Reading and Studying the lives of the Companions

8. The Salaf of this ummah: the Companions of the Prophet - and their students and successors are the best of all generations.
They have the strongest eemaan amongst the people and are the most well grounded in knowledge.
They received the religion from the Prophet and it took root in their hearts. It suffices as a representation of their excellence that Allaah addressed them with His saying:
"You are the best people ever raised up for mankind..."
[Soorah Aal-'Imraan (3): 110]
The meaning of which is, you are the best of all peoples and the most beneficial for the people.

9. In Saheeh Muslim, Aboo Hurayrah, reports that the Messenger of Allaah said:
"The best of my ummah, is the generation that I have been sent in, then those who proceed after them ..." [Muslim]
It is also related in both Saheehs by 'Imraan ibn Husayn with the following wording:
'The best of my ummah is my generation, then those who proceed them...
One who studies the condition of these righteous people, reads their biographies, perceives their sublime qualities and virtues and reflects on what they were upon, such as the tremendous character and mannerisms they had; their adherence to the noble Messenger , their fear of sins and disobedience; wariness of riyaa' and hypocrisy; can not help but develop love for them and want to be like them in faith!