In France it’s considered flashy to tip for no good reason. In restaurants you will see the phrase ‘servis compris’ on your bill. This is the 15 percent service charge required by French law for taxation purposes – which your waiter might never see, so if you’re happy with the service you can always add a tip with a few coins or by rounding up the bill.
In bars it’s not generally the custom to tip at all.
Tipping in taxis isn’t obligatory, although most people do tip a small amount, often rounding up to avoid the hassle of dealing with fiddly coins.
In hotels, tipping is entirely at your discretion with a few Euros being standard.