Did this myself about 18 month ago & still going the sole trader route. A few pointers:

- Decide whether you want/need to register for VAT
- Keep a separate bank account for the business to your personal account
- Remember not to spend all the money! If you start trading in (say) Jan 2016 you won't have to pay a penny of tax until October 2017, it often disappears!
- Keep receipts for everything you buy/do business related - its generally tax deductible!
- Log income & expenditure (even if its a simple spreadsheet) - it will be easier when you have to do your tax returns
- If you're not comfortable get a good local accountant to prepare your accounts & tax returns from your excel spreadsheet - €300/€400 well spent

If you have any questions, feel free to ask!