In coastal towns, seagulls make pigeons appear very small and innocuous. Gulls are large, determined birds and remarkably good at ripping open garbage bags to get food. This, of course, looks extremely messy. It is also unhygienic. Household garbage scattered all over the place attracts insects and rodents. To stop seagulls creating miniature landfill sites next to your home, make it impossible for them to access the bags in the first place.
Store garbage in a shed or garage in sealed bags until collection day, if possible.
Purchase gull-proof bags. There are different versions, one of which is a large mesh bag in which you place up to three normal trash bags. Such bags are straightforward for refuse collectors and householders to open, but inaccessible to gulls.
Place heavy rocks on the lids of dustbins or secure the lids down with rope. Wrap the rope underneath and over the can once or twice and tie firmly. Other scavenging animals, such as foxes or raccoons, often get into unprotected cans, leaving them wide open for seagulls to make even more of a mess.
Replace old cans with animal-proof ones. These are often sold as "raccoon-proof" or "fox-proof" dustbins and they keep virtually all scavenging wildlife out, including gulls.
Life-size plastic raptors, such as owls, eagles or hawks, attached somewhere visible may or may not deter gulls. There is no harm in putting one up if you like such things, but it may not work for longer than a few days, if at all.