Full disclosure: I've not completed the ISEB certification, however prior to moving to development I managed a QA/Test team of 5, two of who had completed the foundation certification.
My suggestions are:
Remember, this is similar to every other qualification that you've ever done so the same basic principles hold true:
Plan: Put together a study plan so you know what you should be studying and when. You need to ensure that this is achievable in the time you have available
Organise: Keep yourself organised. If you're a lists person, write lists. If you like using your Outlook calendar to organise yourself, put all your study periods into that.
Keep Notes: Lists, brainstorms, bullet points, paragraphs, flowcharts; whatever works for you to act as a quick reference that helps you refresh your memory.
Balance: This does tie back to "Plan" to an extent. Don't over work yourself. This isn't school, college, or university, you're holding down a full time job and studying. Make sure you strike the right balance because if you don't, studying for ISEB will make you miserable. That isn't likely to result in a good grade.
As far as the ISEB is concerned, it has been known to be called a little, errr, "dry". PersverePersevere though, it does add value to your day to day working skillset.
- Can you find opportunities to introduce things you're learning into your day-to-day role? There's no better way to reinforce theory than practice (If you can't, why are you studying towards it?).
- Do you have any colleagues who're certified (ISEB that is, not the other certified! =) and can act as a sounding board for ideas or to help you grasp concepts you may struggle with?
- Don't forget, now that sqa.stackexchange exists, there'll (hopefully!) be a lot of people here that you can apply my prior point to.
Whilst none of this is particularly specific to ISEB, hopefully it'll be of some help to you in your studies!