We've organised and been on several trips, travelling independently by train and ferry. I've developed a few 'rules of thumb'. You may not agree with them all, but I hope they give you food for thought.
I'm a huge fan of compression travel cubes - they save space, but more importantly, allow for organisation in a packed suitcase.
Save those socks and pants that are developing holes or where the elastic is losing its twang and take them on holiday - instead of bringing them home to wash, throw them away after you've worn them! Same applies to face clothes when they eventually become see through!
Travel specific clothing dries quickly - wash it in the shower or hand basin using hand soap. Hang it up and it'll be dry in the morning. I've carried a travel washing line with me for years, but only used it once. To speed up the way clothing dries you can get much more water out of it by wrapping ittowel and wringing it hard.
Buy a genuine Palestinian Keffiyah - they're available in all sorts of colours and patterns. One can be used for bed sheet if a duvet is too warm, or a scarf if the day gets chilly, or you need some sun protection. At a push, a keffiyah can even be used as a bag!
Check the validity of tickets etc - avoid embarrassment by checking and double checking (eg some German train tickets are only valid on local trains). Double check the dates on your seat reservations and tickets - it's easy to get tge month (or year) wrong!
Travel first class if you are buying an interrail pass. There's much more space, less likelihood of having to stand, and sometimes there's free food or drink (not often, but....) If you have a UK Disabled Railcard then your companion gets a free interrail pass - honest!
When journeys go wrong don't take it out on the staff - they don't want to be providing a rotten service. They may be dismissive or unhelpful and that's inexcusable, but whatever the problem is, it's not the fault of the guard, conductor, or the platform staff. Don't be an abusive asshole.
Hotels very close to railway stations should as a very general rule be avoided, particularly if you intend venturing outside after dusk. For some reason, stations attract the less savoury elements in society. There are of course huge exceptions to this statement, but be alert!
Hotel breakfasts are expensive but worthwhile because it's easier to just eat first thing, than try to find food outside the hotel. If you are bold enough, it's often possible to drop lunch into your bag from the breakfast buffet too.
Build in rest days. Collect your thoughts. Rinse out your smalls. Chill.
Even a bad sketch will help you remember somewhere more than a dozen photos ever will. Search 'urban sketching' for hints on how to start (but don't over think it).
You can't buy memories. The silliest trivial things will be what you remember about your holidays. Enjoy your trips.