First visit in Paris!

You do not need a tour agency, unless you are handicapped or very elderly.

You can do most of this yourself by Googling official websites, seeing what's open on which days...
You should also pull up a Google map of Paris, to see where the attractions you are most interested in will be.
Nobody can tell you what you will want to see, unless you let us know what your interests are.

What time of year are you visiting and what is your budget in euros?

Why not start right here, on this very website: https://www.ricksteves.com/europe/france/paris

chexbres is spot on: Paris is a very easy city to do without a tour agency - we spent a week there and planned it all ourselves - but you need to spend some time with some guidebooks and the link Southam has provided as well as the city's tourism website: https://en.parisinfo.com

There is a ton of stuff to see but one person's must-do can be another's must-miss so you need to pick and choose based on your own interests versus someone else's.

Also, the more information you can provide, the more the good folks here can help you: ages of travelers in your party, interests, budget, time of year, length of stay, etc.

Editing to add: I see that you've picked up some ideas in the "Best memories of Paris" thread. :O)

https://community.ricksteves.com/travel-forum/france/best-memories-of-paris

Paris has so many diverse things to do and see that it's impossible to make recommendations without knowing your interest, amount of time available, and the time of year you will be there. Suggest you pick up a copy of the guide book for Paris published by Rick Steves. Go through it cover to cover, see what strikes your fancy, lay out a "rough draft" of your plan, and go from there by seeking specific advice about specific things. Oh, and you do not need a tour agency. Paris is very user friendly even to newcomers.

For my first trip to Paris, I started out by printing out the sights listed for Paris Museum Pass. I looked at websites for them and decided which I wanted to see. I then went to Google maps and save each one I wanted to see (click on the star on the left of the page to save). After that I went to TripAdvisor and looked at their top things to do (at least a few pages), and saved the ones that looked interesting on Google maps.

Google maps will show the open hours for each place you click on. Remember hours change for different times of year, but it gives you a good idea which day each place will be closed.

Once I had that, I sorted them into a groups, on the map, so I could have walkable days. I decided which day would work for each group based on opening hours and closures.

I really like the pass because it allows you to stop for 30 minutes at a small museum that might not otherwise be worth paying a seperate admission.

Be realistic about how much you can see in a day. I try to limit museum visits to two hours at a time and focus on a part of the museum rather than spend all day trying to see everything. I also limit how many stops I'll make. Generally, I'd say one big sight in the morning and one in the afternoon is plenty. The nice thing about Paris is you can do that, plus a couple smaller sights that are within walking distance, without feeling overwhelmed and still have evenings to relax in a cafe or stroll.

I commend Brad for such a logical approach. Maybe I will adopt it. I've tended just to circle things on a paper map.

For my first trip to Paris, I started out by printing out the sights
listed for Paris Museum Pass.

Great idea, Brad! This method would work especially well for the Paris Museum Pass, I'd think, as it's generally an outstanding bargain depending on what you want to see and how much time you have.

I really like the pass because it allows you to stop for 30 minutes at
a small museum that might not otherwise be worth paying a seperate
admission.

It's also useful for breaking up large, time-consuming places into more easily swallowed bits, such as the Louvre. You may revisit the attractions the pass covers as many times as you wish as long as it's within the period of validity so we used our passes for three separate visits to the Louvre, including popping by for an hour or two during a late-opening night. You could also, say, go up to the top of the Arc de Triomphe once during the day and again after dark for different perspectives.

Also, people tend to always go places where they climb to a summit to look out. Don't do too many activities like this.

For example, L'Arc de Triomphe, to me, has one of my favorites views because you can see many of the monuments from it. Same with la Tour Montparnasse.

The view from the Eiffel Tower isn't as exciting to me because you can't see the tower. But you definitely should go to the tower to see it.

It all depends on what you want to see.

But if people don't especially like museums, that leaves a lot of other things to do.

When starting to prep for a visit somewhere I usually check Trip Advisor first to get an idea of things I may want to see (aside from the things I already have in mind) to get a rough idea of days needed. I get my RS book at some point but TA is especially useful at the very beginning.

I travel solo and do all the planning myself, no need for a tour agency. Everyone's must-sees are different--for me, it was going to the summit of the Eiffel tower, visiting Versailles (enjoyed the Trianons and Hamlet area far more than the palace), a flea market and certain museums. My 6 day stay was perfect for a first visit and allowed plenty of time to wander and explore. Get a Paris Museum Pass and get comfortable with using their public transit are my 2 bits of advice.

My first time to Paris I was 21 years old. I used my Rick Steve's guide but I also booked a tour with Paris-trip. Why? I wanted easy access in a few days to some key sights. It took a tour that started out with a city ride that made a few photo stops (Notre Dame, Sacre Coeur) and then it ended at the Eiffel Tower where we got to bypass the line and it included lunch at 58 Eiffel and a Seine River cruise. The guide was excellent and I really enjoyed my first day in Paris. This trip was helpful because it gave me my bearings and it got the Eiffel Tower experience completed (it was another 10 years before I went up again) and made everything rather pain free. I was then comfortable enough to venture out on the metro and discover the city solo. Now I rarely ever take tours, but it did ease me in.

We just got back a few weeks ago. I did a lot of reading and research to decide what we would like to do. We are more outdoor seeing the sites, exploring the neighborhood kind of people rather than spending a lot of time in museums, although we did pick two that we wanted to visit. We arrived and checked into our hotel early afternoon, so that was when we went to the top of the Eiffel Tower, since it was my bucket list item. Spent the day walking the riverwalk and just getting our bearings. The next morning we did a a small group electric bike tour which took us through areas that we might not have found on our own. It was nice having a Parisian to ask questions and get information from. We felt that it was a great way to acclimate to the city. We find that making a list of thing we would like to do is helpful but then each evening we would plan for the following day based on what we did that day, the weather, and what we were in the mood for. We would often leisurely walk and explore for hours, then hop on the metro to make our way back. You will have a wonderful time, Paris is a beautiful doable city.

But if people don't especially like museums, that leaves a lot of
other things to do.

Very true...in which case I probably wouldn't buy the Museum Pass.

How long are you staying, what time of year are you coming to Paris, and what is your budget for hotels and meals in euros?