It is your responsibility as a tenant to look after the general everyday maintenance of the property and the appliances.
Lights not working: first check whether it is just one light or the lights in the whole property. If it is just one light, or the lights in one room only that are not working it is likely to either be a light bulb that needs replacing or a tripped fuse for that area of the house. As a tenant you are responsible for purchasing new light bulbs. It is a good idea to have a spare available for those last minute emergencies. If you do not know what type of bulb you need, most DIY stores will be able to help you identify the right one if you take the old bulb with you. If the fuse has tripped you should be able to simply flip the switch in the fuse box to regain the power for that room/area of the house.
Vacuum Cleaners: all vacuum cleaners will need to be emptied regularly to ensure they continue to work efficiently. Depending on the model of vacuum cleaner you may have to buy replacement bags for collecting the rubbish most supermarkets will stock the well known brand bags. For less well known brands you may have to purchase these directly from a brand website. Some vacuum cleaners are bag-less and can be easily emptied into the bin. You should be provided with any instruction manuals and should ensure you maintain the upkeep of any appliances.
Blocked toilet: You should take initial action to try to remedy the blockage. Try using a toilet plunger. If this is unsuccessful you should contact the landlord or agency to report the blockage and request a plumber to visit the property.
Blocked drains: You can buy reasonably inexpensive products in most supermarkets that are designed to help with blocked drains. If this is unsuccessful then report it to the landlord or agency for further investigation.
Condensation/Mould: As a tenant you should take steps to reduce any opportunity for mould to grow. You should try to keep the property well-ventilated and take particular care if drying clothes inside. You should clean away any surface mould as and when it occurs but keep records if it continues to return and report any larger mould issues to the landlord as soon as they occur. Mould can be caused by dampness in the air if the property is not well ventilated but may also be a sign of larger more structural issues.