If you don't have a window cleaner, simply use water and dry afterwards. Individuals can also use newspaper, but its not recommended if you don't have to.
Hand wash your vehicle if possible. Going through automated car washes will create swirling effects in your clear coat. They are applying dirt from previous cars onto yours, and can also create watermarks from incorrect drying.
If you have a stain on the fabric of your interior but don't want to get it detailed? Try mixing hydrogen peroxide 6% as a 2:1 ratio. For every 1 part of hydrogen peroxide you will need to have 2 parts water. This is a great way to break up stains. Once mixed, spray as a mist across the area needed, and use a towel to scrub it after about 5 minutes. Just a cap full in your wash cycle will help remove blood from clothing as well.
We don't recommend PPF for vehicles. If your car gets a ding or scratch from debris, it will protect your clear coat to a degree. The issue with those is having to completely replace an area of PPF if that happens to remove the imperfection. We highly recommend wax or other various coatings in place of PPF.
If you have recently purchased a new vehicle or are planning to, getting a Ceramic coating done will keep your investment lasting longer.
If you are looking to resell your current vehicle or trade in towards a new one, getting a detail prior will increase your asking price significantly. This same logic applies if you're looking at the car you may replace it with. If you notice swirling, water spots, stains on the inside, any noticeable defects to the paint or interior overall then you have great leverage in your favor to decrease the asking price of the seller. Especially if you mention you would have to get it detailed to fix the findings.