This is pretty simple. Either:

1) when your wife finds a job, the employer will fill in the paperwork to apply for a National Insurance number, enter her into the tax system etc,

or

2) you can send your wife to the nearest Job Centre Plus, at which she can apply for an NI number.

If your wife is a "white collar" professional, then (1) is really quite simple, otherwise (2) is simple for everyone. She will need to take her passport and proof of address. To get proof of address you can:
a) open a bank account. Major high-street banks, e.g. Barclays, HSBC, are pretty good about accounts for new residents (my wife got her account after 3 days in the UK)
b) add her to your council tax bill (you're legally obliged to do this anyway)
c) declare her to the electoral register (you should do this anyway). The Electoral Commission will send a letter by return stating she's ineligible to vote: keep this.

Oh, and finding a job: it depends on her line of work. If her present employer is a multi-national company, they might just transfer her to a UK office. If she's an engineer, I can recommend a few agencies. Otherwise, the Telegraph on a Thursday (job ads), or local employment/temp agencies.

 

We used a council tax bill to open my wife's account. I wrote to my local council informing them of a change of occupancy of the house (which I had to do as I was claiming the single-resident discount before): they returned an updated council tax bill in both our names. This was sufficient to open the Barclays account.