doubt (in regard of the path, the Gems, Nibbana, that escape is possible) actually ends only by entering the stream, by having seen for oneself. Till then doubt will be ones attendant.
So for the whole practice Saddha, confidence, faith, is most necessary. The transcendent depending co-arising, pointed out by the Sublime Buddha, gives Dukkha (suffering, stress) as cause for the arising of Saddha. So if one has heard the Dhamma of the Arahats - knows that the six senses, there objects, what ever arises on touch on them, are not real, insecure, subject of change, no refuge, not worthy to regard them as mine, me - does well to always keep that in mind and let fear in regard of the world not fade, nourishes, next to Saddha, Samvega.
Conditions and detail points to nurish a urgency and doubt in regard of the world are already given in other answers (see Upasaka Maga2020 answer), dealing with the fetter in- and of itself.
So generally the way to increase Saddha and cut off doubt is lesser a matter of desire for certain happiness at first place, but to face Dukkha to gain a drive. The lesser ways to seek after other kinds of happiness in the world, the five senses, the more certain (reminded onthe good Dhamma) that one get's fuller aware of suffering and as the original word of Saddhā derives form Saddh(a), sacrificing, giving, letting go, beginns to let go of the causes, the world, the senses. Having now an escape known, if reminded, the entering of the stream can be quick, very quick, and with it douts are abounded. They may still temporary arise but can no more lead to real bad action, kamma.
Outwardly, like always in this heritage heard, is there nothing more conductive then association with wise, real 'friend' and to withdraw more and more from 'bad' friend, lower or equal in virtues.
May good householder therefore find, after seeking wisely, be/do always near association with the wise. May he not go after, seek, after fools, especially doubtful natures, avoiding them like a sickness's cause.
[Note that this isn't given for stacks, exchang, what ever other world-binding trade, but for release from dout, for ones key to escape]