I would note that the perfect place could be ANY place that inspires you. I often paint from the back of my SUV because the tailgate raises and creates a nice sunblock and table space for supplies. But there are times when the perfect place may be on a sidewalk, on a boulder, a grassy knoll, a beach, or in a forest. You need to be prepared. Fortunately, it is not complicated or expensive to get started.
My first plein air pochade box was a cigar box mounted to a tripod. Pochade is a French term for pocket and refers to a small box for capturing the colors and atmosphere of a scene. My old cigar box was actually quite perfect for small paintings. It would hold a 5x7 or 6x8 size perfectly inside the lid. It could hold an 8x10 canvas too if it was not too windy.
I spent about $17 for a tripod mount from Amazon and found an old lightweight tripod in a second hand store. I went to the art store and got some palette paper (you could probably use wax paper instead of palette paper) and 1/4 inch thick foam core. Anyway, cut the foam core to fit inside the cigar box then, wrap it with the palette paper. Place small tubes of paint or pastels in the bottom of the box and place the foam core palette on top and "Voila!" You have a perfect little lightweight plein air pochade for under $30. You could use this for pastels, acrylic or (in my case) oils. FYI, a typical pochade setup is $200-$400.
I quickly outgrew my cigar box pochade because I like to paint on bigger canvas. But I still use it occasionally for small quick projects and demos.
There is more to consider when gearing up for a plein air adventure. I like to be out for most of a day when I go and need to be prepared. I bring water! Staying hydrated is VERY important! Because I am obsessive, I forget to eat or drink at times when in the throes of inspiration. I often bring protein bars or other lightweight food. Also, If using acrylic bring a brush wash container and separate bottle of water for that purpose. Mark it clearly because I have absently picked up paint water and drank it. That will quickly & rudely un-inspire your painting! Yuk!
I use oil so I initially made a brush washer to hang my mineral spirits from my pochade box. It was just a plastic jar with a lid and some wire mesh inside up-cycled from a bouillon cube container. Attach wire or string around the neck to hang it from your box or tripod. This would work for acrylic brush water too.
I have an array of attachments to my tripod which is probably overkill but I was a girl scout and am always prepared. I attach paper towels, palette knives, brushes, compass/whistle, & water. Remember that lightweight aluminum caribeaner and 'S' clips are your friend! I like to clip everything to my tripod. It is handy, stabilizes my tripod and is off the ground so I don't have to deal with picking up sand, dirt, slitherers, or multipeds creeping into my equipment bags. Ugh!
Speaking of bag, most plein air artists use a backpack or camelpack to transport everything to their site. I think that is quite perfect for those trekking some distances from their vehicle. I don't really do that very often. I have a small compartment bag that holds my brush washer, brushes, lunch, water, radio, colorwheel, extra paints, paper towels, and whatnots. The bag is relatively small because, like most women that I know, if you have room in a bag, you will fill it. This bag has a clip that I use to attach and hang from the center of my tripod for added weight & stability. I have a large overnight bag with an over shoulder strap that holds the small bag, the pochade box, my canvases, and tripod. I try to make the entire bag as lightweight as possible. Believe me, when trekking more than half a mile from your vehicle, every ounce counts!
To reduce weight, I leave extra paint in the car. I make a point to set up my palette before I go out to paint. I generally squirt my paint onto my palette in order of my color wheel - dark to light. Regardless of how you set it up, just do it the same all the time. It makes it easier to find and mix your colors quickly especially when trying to work in changing or failing light.
If you are a beginner, use a limited palette. I like a lightweight palette of 5-7 colors and from that I can mix nearly everything I may need. Those are Burnt Umber, Ultramarine Blue, Alizarin Crimson, Cadmium Yellow and Zinc White. I do add a few other colors (like a warm red or ochres) depending on where I am painting and the time of day but mostly everything can be done with a dark brown, a blue, a red, a yellow and a white - each of your choice.
Also, you should try and notice how the light changes every 15 minutes or so when you are outside. Note the shift in shadows. Note the color and intensity of the shadows. Do shadows have the hard edge of a cloudless day or the softer diffused look of an overcast sky?
Try to get the sketch of your painting on the canvas within 15 minutes. Use light paint. I use the yellow to sketch because it is easily covered and changed as you adjust your perspective.
Finally, take a picture with your phone after you finish your sketch. You may want to add in some details when you get home.
Just paint. Then paint more. The more you do, the better you get.
