We found a rat in our house (or something else like that)!!

Alert the landlord as soon as possible during regular business hours. He or she should take immediate action (traps, poison) and, if the landlord does not, call the Building Department. Meanwhile, remove all possible food and water sources for the rat. This means properly dispose of all kitchen waste and garbage; check the food in the cupboards to see if any packaging is gnawed and dispose of the contents; secure foods in glass or metal containers. Never forget to put your garbage out!

We want to paint our rooms

Before you alter anything, you must get the permission of the landlord. Commonly, landlords either offer or can be persuaded to provide paint and materials if the tenant offers to provide all the labour. The landlord may balk at vivid colours unless you agree in writing to return the walls to their original colour--at your own full expense--before vacating.

Paint is peeling in the kitchen

Alert the landlord. Underlayers of peeling paint can contain lead; regardless, you don't want any type of paint chips contaminating your food preparation/eating area. Peeling is especially a problems in rooms with high humidity, so unplug the kettle as soon as it's boiled and put a lid on pots of boiling water. In the bathroom, there should be a functioning fan or a window that can open; use them to dissipate the humidity.

The caulking in the bathroom needs replacing

Another--urgent--job for the landlord. The black stuff that grows around the tub is mildew or mould and people, with no prior allergy, can develop an allergic reaction over time. Or, if the problem is that there is caulking is missing, water goes in the wall...and can ruin the ceiling below.

We want a new lock on the front door

Speak to the landlord. You want a solid deadbolt lock and receiving panel--both mounted on a solid-core door and solid doorframe. If you already have these but you want the lock changed so that former tenants cannot have access, you may have to pay some/all of this cost. Regardless, before you change the lock you must get the landlord's permission.

The landlord doesn't respect our privacy

The landlord should provide 24 hours written notice of any intent to enter the premises--excepting emergencies. However, it's common for a landlord to call a few hours in advance ("I'm sending the plumber at 2 pm, okay?") and if you accept this (which you probably would) then the notice is waived. If the landlord is giving no notice, call/write the landlord and, politely but firmly, insist on appropriate notice. Appointments should be during reasonable hours; some workers arrive as early as 8 a.m.--but at least they arrive!