Create an itinerary and pack clothes according to it to avoid overpacking. Search about the places you will visit and select your outfits based on the weather.
Consider taking shoes that are versatile and can match the majority of your outfits. Shoes occupy a lot of space in bags.
Always keep your toiletries in travel-friendly mini bottles in a different pouch. Make a small-sized pouch for your essential medicines.
Try to carry 1 or 2 hair tools that are used more often. Nowadays, hotels generally provide hair dryers, you can confirm the same with your hotel beforehand.
If you are travelling to a cold place, try keeping fewer coats or jackets as they utilise a lot of space. You can also shop for them at your destination since colder climates normally house the best options.
Keep your heavy items at the bottom and then layer them up with lighter stuff. Consider using all the pockets of the bag smartly.
Always consider keeping your documents in a separate folder and a separate pocket to prevent them from getting lost during the trip.
To avoid inconvenience while coming back from a trip, try keeping some space in the bag for new items purchased from there.