The easy and simple way around Paris is to walk. Not only will you get some good exercise, but you will be able to take in all the senses and sounds of the city as you move between the various tourist attractions.
Naturally, if you need to go some distance, you're tired or the weather is bad, you can take the Metro. This will take you close to where you need to go with minimum hassle and speed. It goes without saying that you will miss out on the atmosphere that comes with a stroll through Paris streets, and the congested stations, long corridors and the many stairs can be trying. Still it is hard to beat for sheer convenience.
Do remember if using the Metro that you may encounter the unpleasant side of public behaviour. You may see somethings you would rather not, and you will need to be extra vigilant of your personal security. Pickpockets working in gangs are a constant scourge and work with such impunity that at this stage they should be accorded some form of official recognition in the form of franchise or licencing.
Take special care of your wallet, handbag and mobile phone. These predators are waiting for a tiny chink of opportunity and they will have your property off you in a flash. Aside from all that, you'll be fine.
And one other bit of common sense advice ..... Do check for any savings you can find before you travel and before you book. Accommodation will be the biggest expense, so I recommend you check out our Paris hotel deals which will bring you to a wide choice of discounted hotels within the city. That way, the enjoyment of your trip has already started before you have even left home.