Its always hard to give specific advice on adwords campaigns without really looking at them but here are a few pointers.
1) Do you have your adgroups split into various campaigns or it is just one campaign with a bunch of adgroups or (Worse) one campaign with one adgroup with a single massive list of keywords!
2) Start by breaking up your keywords into Campaigns. How you break them up is always a matter of what works for your business. One obvious campaign would be Xmas related adgroups. Then you could pause that adgroup after Xmas and restart it again when the xmas season starts up again. Picking your campaigns is all about giving you control on the budget you then want to spend on the adgroups and keywords you put into the campaign. There in nothing stopping you having one campaign per adgroup as that will allow you to set a budget for each adgroup!
3) Right, now you need to set up your adgroups properly. For this you really need to group them into highly related keywords. Here's the first
Beating Adwords video that explains that.
4) Once you've got your adgroups set up, take a look at your ads. An ideal way to go for cheaper clicks is to write
Keyword Targeted Ads. Write at least two per Adgroup so that you can test which one is best.
5) Now for conversions. You need to make sure the landing pages you are sending people to are 1) Optimised for the keywords in you Adgroup, 2) Written to convert!. The copy on your landing page is critical. You've got to grab their attention with the title and first line. People generally decide whether to stay or leave within 8 seconds.
There's just a few quick tips.
Hope that helps.
Cheers
Mike