For a government to be elected, it must have a strength of at least half of the total strength of the assembly. If these particular criteria aren't met, any member can initiate a no-confidence motion against the government and this does not require any reason, and the speaker accepting the no-confidence motion means, voting is the only way to prove majority. Lok Sabha is elected by people and hence only there a no-confidence motion can be passed, and not in Rajya Sabha.
Under section 198 of Lok Sabha, there are guidelines for passing no-confidence motion. The person wanting to initiate a no-confidence motion must inform the house speaker in written format before 10 am, following which the speaker will read it out to the ministers and other members of parliament, and a no-confidence motion requires at least the support of 50 members.
Within 10 days of the acceptance of the no-confidence motion, voting must be conducted, besides the debate on the decision. If the government isn't able to prove its majority in the voting, it must resign with immediate effect.