Paris to Charles de Gaulle airport in June

Same as any other time. Private van/taxi/public transport. Routes depend on where you are starting and what you want to pay. Many tourists ride the RER B suburban train from Gare du Nord. Do your research at http://ratp.fr/en/ratp/c_5000/accueil/ and www.aeroportsdeparis.fr This question arises all the time and the Internet bristles with answers.

Best as in cheapest and fastest, or best as in easiest. If you wish easiest take a taxi, call one night before, G7 has English speaking operators. Or if at a hotel they will usually call one for you night before. If you call a taxi it may arrive with a few euros( up to 5-7 already on meter as they put meter on from wherever they get the call.
Drive to airport can take between 40-50 minutes , depends on traffic, you should leave Paris by 7:15-7:30 . Its good to be at airport about 3 hrs in advance.Total cost may be between 45-55 euros, depends on traffic, how many people ( extra charge of 3 euros per person over 2 people, and one euro per suitcase in trunk, these are off meter charges) You could also take RER, 10 euros, takes 35-45 minutes. They leave often, like every 10 minutes or so.. maybe even less. Trick with RER is getting to RER station ( depends on where you are staying, where are you staying) and if you have a lot of luggage or small children to deal with.. there are often stairs in metro stations and long passageways to walk, but if you are near a direct station its pretty uncomplicated.

Definitely plan on being at the airport 3 hours before your flight! Where I'm staying in Paris makes a big difference in how I get to the airport - by what metro station are you nearest? Or, just give the name and/or address of your hotel.

We took the train into Paris from airport and had difficulty because of stairs. We each had a large suitcase, a carry on, and a backpack. We were two levels down. Walking up two long flights of stairs was impossible for us. We were fortunate in finding an elevator, but do not think they are common.

Our hotel staff arranged for a shared van at a cost of 38 euros. We were the only people on the van, so it was like riding a taxi but for less money.