Paris use comparable modes of transport as London, the Metro or RER Réseau Express Régionale (Regional Express Network) are Paris’s equivalent of the London Underground/ Overground and are very similar by approach. A one day travel card can be purchased from the many machines in nearly all the stations. RER connects central Paris with the outer regions and is the easiest way to and from the airport, it has 5 lines RER A,B,C,D and E. The Metro or Metropolitan on the other hand has 16 lines. In my experience the train systems are quick and convenient and relatively cheap, it gets you from A to B in ordinary fashion and although most of the times there are no seats, it is not as busy as other countries I have been to. On the plus side there is plenty performers or buskers inside the trains, it is something different and although the locals careless about them it is good for tourism.
There are buses and taxis however I mostly just used their Metro or RER because like London many points of interests are not far from stations. So I cannot really write about them.
Alternatively if you are fit enough walking around parts of Paris is not such a bad idea, as long as you know where your going and can navigate the city is not far apart.
Overall for me roaming the city was easy to do just by using the rail systems and by walking. However if you have a bit more money to spend then taxi’s would be your obvious choice for comfort.
Reference Photos metro map (https://www.flickr.com/photos/deepakg/6148932631)