EE, O2, Vodafone, T-mobile, Orange
First, the bad news - in the UK at least, there's at least a month to wait until the phone goes on sale. Samsung has officially said the 26th of April, assuming enough handsets can be produced in time and there are no manufacturing issues, like the ones experienced by HTC for its One smartphone.
You can't even walk into a shop and put your money down, as pre-orders don't kick off until the 28th of March. However, that doesn't mean you can't join the queue today: all the major network providers, online retailers and high street stores have set up web pages for eager customers to express an interest.
Currently, EE's landing page will let you express an interest in a 4G contract, or a 3G contract on either Orange or T-Mobile. If you want a Galaxy S4 on 4G at launch, EE will be your only choice.
EE's Galaxy S4 landing page - the only place for 4G right now
If you're prepared to wait, Three will sell the Galaxy S4 as on a 4G-ready Ultrafast contract, which will automatically tick over from DC-HSPA+ 3G to faster 4G speeds once its LTE network is switched on. It won't cost you any extra and you won't need a new contract or SIM card, so the process should be pretty painless.
Three will get 4G soon, but not by the time the Galaxy S4 launches
Vodafone has set up a landing page for the Galaxy S4 on its website homepage, where it is listing the phone as 4G-ready. However, unlike Three, its possible that 4G will cost you more than a 3G contract. Vodafone's blurb says that once 4G arrives, "we can talk about adding Vodafone 4G to your monthly plan" - suggesting you'll need to talk to the company rather than having everything handled automatically.
O2 is still refusing to reveal the details of its planned 4G rollout, but if you're just interested in the phone and not faster mobile broadband, you can express an interest in the Galaxy S4 on the generic Get Updates landing page.
HIGH STREET STORES
If you'd rather visit a bricks-and-mortar shop to pick up a Galaxy S4, you can pre-register at both Carphone warehouse and Phones4U today. Although neither company has yet to reveal details, it's a safe bet that both will be selling the phone on a range of contracts from all the major network providers, as well as the range of official accessories.
The carphone warehouse Galaxy S4 landing page...
...and the Phones4U page.
Finally, if you're looking for a SIM-free handset, online retailers Expansys and Cloveboth have Galaxy S4 landing pages.
Unfortunately, none of the links we've posted here give us any clue about what you'll have to pay for a Galaxy S4 once it goes on sale - as it will compete with other 5in, Full HD smartphones from the likes of Sony and HTC, expect to have to pay upwards of £40 a month on a two year contract if you want to get the phone for free. Once prices have been confirmed, we'll be sure to update this article with the latest deals and contract offers.