Alright from an islamic perspective, we give da'wa not only because we want to establish Allah swt's deen wherever we go, but for us as muslim's calling people to islam is an obligation.I mean in surah an-Nisaa, its says: 'Invite to the Way of your Lord with wisdom and fair preaching, and argue with them in a way that is better. Truly, your Lord knows best who has gone astray from His Path, and He is the Best Aware of those who are guided.'
How you ask?
The best form of da'wa is undertaken by example as opposed to preaching.
When we call people to Islam, we must remember to do so with kindness, gentleness, honesty, compassion, patience, and most importantly with knowledge...one cannot invite people blindly without proper knowledge, proper understanding of islam..there is even a verse, where Allah swt commands the Prophet (saw) to say, 'This is my way; I invite unto Allah with **sure* knowledge...'* (12-108).
Here's something i wrote in answer to another thread a few months ago..
'Inviting people to our places of worship, allowing them to take part/witness our celebrations is a means of showing them islam. Islam does not 'bribe', it does not take the missionary..(ie.evangelistical) approach of christians, to illustrate this point we need not look further than our own backyard...the natives in north america...even south america for that matter.
There is NO force in islam, a desire to believe has to come from within, and faith...IMAN can only come from Allah swt.'
Da'wa is not preaching, its not criticizing...it is showing, by not only our words, but our actions, our manner, our character, our example.
'And who is better in speech than he who invites to Allah and does righteous deeds, and says: 'I am one of the Muslims.'
(41:33)