Sure, visiting the charming cities of Warsaw, Radom, and Plock in Poland can be an exciting adventure. Here are the travel tips for your journey:

Best Time to Visit:
The best time to visit Poland is during the late spring (May) and early autumn (September-October). During these times, the weather is generally warm and there's less crowd compared to the peak summer months.

Route and Accessibility:
Warsaw, Radom, and Plock form a triangle on the map with good road and railway connections. Starting from Warsaw, you can take a train or drive to Radom which would take approximately 1.5-2 hours. Thereafter, Plock is about a 2 hour drive from Radom.

Altitude and Acclimatization:
These cities are at a lower altitude, so you shouldn't have to worry about altitude sickness.

Accommodation and Booking:
Booking accommodations in advance is advised in these cities, as there are busy times due to festivals or conferences. There are ample accommodations options from luxury hotels to budget guesthouses and vacation rentals.

Clothing and Essentials:
The weather can get chilly, especially in the spring and autumn so make sure to bring warm clothing. Rain gear is also a good idea as the weather can be unpredictable. Walking shoes are important as these cities are best explored on foot, and don’t forget a power adapter for your gadgets.

Health and Safety:
EU citizens get free healthcare in Poland, but if you're from outside the EU, have travel insurance that covers health. Poland is a safe country, but like any city, it's advised to be cautious about your belongings in crowded places.

Local Etiquette and Respect:
Polish people value politeness and good manners. Learn a few basic phrases in Polish like a simple Dzień dobry - Good day or Proszę - Please. Respect local traditions, especially when visiting religious and historical places. Dress modestly when visiting religious sites.