If you arrange the price in advance than you’re not expected to tip. If your taxi is going by the meter it is customary to tip around 5% of the amount.
In Mumbai, one driver, after taking me to destination, showed me the note saying that service charge is 5%. Sometimes, taxi driver might try to charge you something extra for the parking or for the highroad which is fine if you really used the parking or a high road.
Sometimes, the taxi driver might be pushy and ask for the tip, feel free to reject.
If you’re happy with the service you can leave anything from 1% to 10%. Some restaurants have service charge included which is visible on the bill. In that case you don’t need to leave anything extra.
Tourist restaurants are more prone to expecting the tip than those serving mostly locals.
The correct way to tip in restaurant is to pay and when the waiter returns with the change you leave the tip. Don’t tell them to round up the bill in advance, that might confuse them.
Many foreigners avoid street food for hygiene reasons but if you are brave enough to go for it you should know that you’re not expected to tip. You can even try to bargain on the price.