The last six months of your time studying your degree is a challenging time, with a dissertation, exams and thinking about what you are going to do after you've finished. It's tempting to put off the job and MSc/MA applications until after the exams. This could be a mistake. Many graduate schemes, jobs and post graduate courses will have been advertised and filled by the time you walk out of the exam room for the last time, so its worth starting your job search early.
To start with you will need to decide what career area/s you would like to focus on, and if you have a specific geographical area you'd prefer. Many graduates will find work within 30 miles of either where they studied or their home address. But a significant proportion find work elsewhere, partly due to where some vacancies are located and partly due to the students flexibility to apply for these vacancies. Knowing how others have used their degree might help you decide, there is more information here, www.prospects.ac.uk/options_with_your_subject.htm. A careers appointment can help you decide about all this.
Students from any degree course can apply for many graduate schemes, with a variety of employers, from retailers, insurers, finance companies, civil service to the police. Some vacancies need some degree relevance, for instance for a horticulture journalist a horticulture degree would be a distinct advantage! Other vacancies will need definite degree skills/content, for instance agriculture for an agronomist job.
Writing a CV and covering letter, either speculatively or in response to an advertised job can be time consuming. But it is definitely worth putting the time in to each one, this is definitely a case of quality is far better than quantity! Be positive, and 'reflect back' to the employer how you meet what they want, www.prospects.ac.uk/how_to_write_a_cv.htm. Many jobs are not advertised, so it is really worth being proactive and contacting employers direct, especially those you have worked for during your degree studies. Surveys often find that students regularly find post graduation work with organisations they have worked with before. This is why working for companies you like the look of, during your studies, can really pay off later. Not only because of the increased chance of an offer of work, but also the experience for your CV and the contacts. Once you have written your CV and covering letter, the careers deptpartment can look at it with you to make sure its as good as possible.
Some jobs will ask you to attend an assessment centre as part of the application process. This can be a daunting experience, but one that is also manageable and can be 'got through' to get to the next stage. www.prospects.ac.uk/interview_tips_assessment_centres.htm has more information. Again, if you going to an assessment centre, do ask to talk it through with the college careers coordinator.
These websites are targeted at graduates/post graduates so have plenty more information and advertise vacancies.
There are more specialist land based sites, which are listed under the general websites list.